Allocated share based compensation granted expense.

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Annual increase in aggregate number of shares reserved for future issuance as percentage shares outstanding.

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Common stock sales agreement amount.

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Number of Stock Incentive Plans

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Proceeds from issuance of common stock net of issuance costs.

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Share-Based Compensation Arrangement By Share-Based Payment Award, Award Vesting Grace Period

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Share-based compensation arrangement by share-based payment award, offering period.

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Share-based compensation arrangement by share-based payment award, periodic vesting, number of installments.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Aggregate number of common shares reserved for future issuance.

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Face amount or stated value per share of common stock.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for option under share-based payment arrangement.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Number of shares issued under share-based payment arrangement.

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Percentage of vesting of award under share-based payment arrangement.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Number of options vested.

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Purchase price of common stock expressed as a percentage of its fair value.

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Number of new stock issued during the period.

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Number of share options (or share units) exercised during the current period.

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Stockholders' Equity - Narrative (Details)						3 Months Ended		12 Months Ended
Stockholders' Equity - Narrative (Details)	Apr. 07, 2022 USD ($)	Mar. 01, 2022 USD ($)	Feb. 28, 2021 shares	Feb. 25, 2021 USD ($)	Mar. 12, 2020 USD ($)	Mar. 31, 2022 USD ($) shares	Mar. 31, 2021 shares	Dec. 31, 2022 USD ($) installment stock_incentive_plan $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Jun. 05, 2020 shares	Jun. 04, 2020 shares	Dec. 31, 2019 shares	Feb. 28, 2014 shares
Class of Stock [Line Items]
Common stock, authorized (in shares)								350,000,000	350,000,000		350,000,000	175,000,000
Common stock, par value (in dollars per share) \| $ / shares								$ 0.00001	$ 0.00001
Common stock, issued (in shares)								184,135,714	177,000,963
Common stock, outstanding (in shares)								184,135,714	177,000,963
Preferred stock, authorized (in shares)								25,000,000	25,000,000
Preferred stock, par value (in dollars per share) \| $ / shares								$ 0.00001	$ 0.00001
Preferred stock, issued (in shares)								0	0
Preferred stock, outstanding (in shares)								0	0
Proceeds from the issuance of common stock, net of issuance costs \| $								$ 7,121,000	$ 88,202,000	$ 209,419,000
Number of stock incentive plans \| stock_incentive_plan								1
Common stock, shares reserved for future issuance (in shares)								27,744,206	26,423,704
Weighted average grant date fair value (in dollars per share) \| $ / shares								$ 1.27	$ 2.29	$ 5.63
Exercise of options (in shares)									0
Intrinsic value of options exercised \| $								$ 0	$ 0	$ 400,000
Fair value of options vested \| $								8,400,000	10,600,000	6,800,000
Stock-based compensation expense \| $								$ 14,652,000	$ 22,735,000	24,460,000
Inducement Award Program
Class of Stock [Line Items]
Number of shares granted (in shares)								435,000
Number of shares outstanding (in shares)								258,000
Stock options
Class of Stock [Line Items]
Number of shares granted (in shares)								3,809,200
Number of shares outstanding (in shares)								11,326,090	11,398,215
Number of shares issued (in shares)			2,833,500
Options expiration after the date of grant								10 years
Stock-based compensation expense \| $								$ 6,800,000	$ 8,900,000	8,500,000
Exercise of options (in shares)								142,440
Intrinsic value of options exercised \| $								$ 44,905
Stock-based compensation expense \| $								$ 6,839,000	8,958,000	8,517,000
Stock options \| Share-based Compensation Award, Tranche, First Anniversary of Grant Date
Class of Stock [Line Items]
Vesting percentage								100.00%
Stock options \| Share Based Compensation Award Tranche One
Class of Stock [Line Items]
Vesting periods								1 year
Vesting percentage								25.00%
Stock options \| Share Based Compensation Award Tranche Two
Class of Stock [Line Items]
Vesting periods								1 year
Number of equal quarterly installments \| installment								12
Restricted stock units
Class of Stock [Line Items]
Number of shares granted (in shares)			2,899,008
Stock-based compensation expense \| $								$ 7,566,000	12,927,000	14,639,000
Restricted stock units \| Share Based Compensation Award Tranche One
Class of Stock [Line Items]
Vesting periods								1 year
Restricted stock units \| Share-Based Payment Arrangement, Tranche One, First Anniversary After Grant Date, Subjected To Individual Continued Service
Class of Stock [Line Items]
Vesting periods								1 year
Vesting percentage								33.33%
Restricted stock units \| Share-Based Payment Arrangement, Tranche Two, Second Anniversary After Grant Date, Subjected To Individual Continued Service
Class of Stock [Line Items]
Vesting periods								2 years
Vesting percentage								33.33%
Restricted stock units \| Share-Based Payment Arrangement, Tranche Three, Third Anniversary After Grant Date, Subjected To Individual Continued Service
Class of Stock [Line Items]
Vesting periods								3 years
Vesting percentage								33.33%
Performance Based Restricted Stock Unit
Class of Stock [Line Items]
Number of shares granted (in shares)								400,000
Stock-based compensation expense \| $								$ 100,000	$ 294,000	464,000
Performance-Based Stock Options
Class of Stock [Line Items]
Number of shares granted (in shares)								400,000	99,558
Weighted average grant date fair value (in dollars per share) \| $ / shares								$ 0.41
Number of shares outstanding (in shares)								400,000	99,558
Stock-based compensation expense \| $								$ 0	$ 0	$ 0
Vested in period (in shares)								0	0	0
Service Based Restricted Stock Units \| Share-based Compensation Award, Tranche, First Anniversary of Grant Date
Class of Stock [Line Items]
Vesting percentage								100.00%
Service Based Restricted Stock Units \| Share Based Compensation Award Tranche One
Class of Stock [Line Items]
Vesting percentage								50.00%
Service Based Restricted Stock Units \| Share-Based Payment Arrangement, Tranche One, First Anniversary After Grant Date
Class of Stock [Line Items]
Vesting periods								1 year
Vesting percentage								33.33%
Service Based Restricted Stock Units \| Share-Based Payment Arrangement, Tranche Two, Following First Anniversary After Grant Date
Class of Stock [Line Items]
Vesting periods								2 years
Vesting percentage								66.67%
Award vesting grace period								1 year
Service Based Restricted Stock Units \| Share Based Compensation Award Tranche Two
Class of Stock [Line Items]
Vesting periods								6 months
Vesting percentage								25.00%
Award vesting grace period								1 year
Restricted Stock Units (RSUs) And Performance Based Restricted Stock Units (PSUs)
Class of Stock [Line Items]
Number of shares granted (in shares)								5,715,808
Weighted average grant date fair value (in dollars per share) \| $ / shares								$ 1.30
Weighted average period of recognition for unrecognized compensation costs								1 year 5 months 8 days
Number of shares outstanding (in shares)								5,668,035	4,554,343
Vested in period \| $								$ 11,200,000	$ 15,400,000	$ 9,400,000
Unrecognized compensation cost \| $								$ 5,200,000
Minimum \| Stock options
Class of Stock [Line Items]
Vesting periods								12 months
Minimum \| Service Based Restricted Stock Units \| Share-based Compensation Award, Tranche, First Anniversary of Grant Date
Class of Stock [Line Items]
Vesting periods								1 year
Maximum \| Stock options
Class of Stock [Line Items]
Vesting periods								48 months
Maximum \| At The Market Equity Offering Program Authorized February 2021
Class of Stock [Line Items]
Common stock sales agreement amount \| $				$ 100,000,000
Maximum \| At The Market Equity Offering Program Authorized March 2022
Class of Stock [Line Items]
Common stock sales agreement amount \| $		$ 25,300,000
Maximum \| Open Market Sale Agreement, Authorized April 2022
Class of Stock [Line Items]
Common stock sales agreement amount \| $	$ 26,000,000
At The Market Equity Offering Program \| Maximum
Class of Stock [Line Items]
Common stock sales agreement amount \| $					$ 65,000,000
2014 Plans
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)														1,785,000
Incremental rate at which the shares reserved for issuance increase								3.00%
2014 Plans \| Inducement Award Program
Class of Stock [Line Items]
Compensation not yet recognized, stock options \| $								$ 8,100,000
Weighted average period of recognition for unrecognized compensation costs								2 years 14 days
2014 Plans \| Performance-Based Stock Options
Class of Stock [Line Items]
Compensation not yet recognized, stock options \| $								$ 0
2014 Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)								4,837,995
Offering period								6 months
Purchase price at the end of offering period								85.00%
Number of shares issued (in shares)								335,146
Stock-based compensation expense \| $								$ 147,000	556,000	840,000
Employees \| Inducement Award Program
Class of Stock [Line Items]
Number of shares granted (in shares)								435,000
Employees \| Restricted stock units
Class of Stock [Line Items]
Stock-based compensation expense \| $								$ 7,600,000	$ 12,900,000	$ 14,600,000
Employees \| 2014 Plans \| Stock options
Class of Stock [Line Items]
Number of shares granted (in shares)								3,233,500
Employees \| 2014 Plans \| Restricted stock units
Class of Stock [Line Items]
Number of shares granted (in shares)								5,219,908
Employees \| 2014 Plans \| Performance Based Restricted Stock Unit
Class of Stock [Line Items]
Number of shares granted (in shares)								800,000
Director \| 2014 Plans \| Stock options
Class of Stock [Line Items]
Number of shares granted (in shares)								140,700
Director \| 2014 Plans \| Restricted stock units
Class of Stock [Line Items]
Number of shares granted (in shares)								95,900
Common Stock
Class of Stock [Line Items]
Common stock, outstanding (in shares)								184,135,714	177,000,963	148,074,085			121,674,568
Issuance of common stock, net of issuance costs (in shares)								4,404,600	26,352,343	24,133,348
Exercise of options (in shares)								142,440		166,633
Common Stock \| At The Market Equity Offering Program Authorized February 2021
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs (in shares)									21,128,065
Proceeds from the issuance of common stock, net of issuance costs \| $									$ 72,400,000
Common Stock \| At The Market Equity Offering Program Authorized March 2022
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs (in shares)						404,600
Proceeds from the issuance of common stock, net of issuance costs \| $						$ 800,000
Common Stock \| At The Market Equity Offering Program
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs (in shares)							5,224,278		3,509,381
Proceeds from the issuance of common stock, net of issuance costs \| $						$ 15,900,000				$ 10,600,000