Recent Accounting Pronouncements (Policies)	6 Months Ended
Jun. 30, 2025
Accounting Changes and Error Corrections [Abstract]
Basis of Presentation	The consolidated financial statements include the accounts of Northern Trust Corporation (Corporation) and its wholly-owned subsidiary, The Northern Trust Company (Bank), and various other wholly-owned subsidiaries of the Corporation and Bank. Throughout the notes to the consolidated financial statements, the term “Northern Trust” refers to the Corporation and its subsidiaries. Intercompany balances and transactions have been eliminated in consolidation. The consolidated financial statements, as of and for the periods ended June 30, 2025 and 2024, have not been audited by the Corporation’s independent registered public accounting firm. In the opinion of management, all accounting entries and adjustments, including normal recurring accruals, necessary for a fair presentation of the financial position and the results of operations for the interim periods have been made. The accounting and financial reporting policies of Northern Trust conform to U.S. generally accepted accounting principles (GAAP) and reporting practices prescribed for the banking industry.
Recent Accounting Pronouncements	On January 1, 2025, Northern Trust adopted ASU No. 2023-08, “Intangibles—Goodwill and Other—Crypto Assets (Subtopic 350-60): Accounting for and Disclosure of Crypto Assets” (ASU 2023-08). ASU 2023-08 requires entities to subsequently measure certain crypto assets at fair value, with changes in fair value recorded in net income in each reporting period, and present crypto assets separately from other intangible assets on the face of the balance sheet and changes in fair value of crypto assets separately from changes in the carrying amount of other intangible assets on the statement of income. ASU 2023-08 also requires enhanced disclosures about in-scope crypto assets and respective activities. As Northern Trust does not hold crypto assets, upon adoption of ASU 2023-08, there was no impact on the consolidated balance sheets or consolidated statements of income.

Recent Accounting Pronouncements (Policies)

6 Months Ended

Jun. 30, 2025

Accounting Changes and Error Corrections [Abstract]

The consolidated financial statements include the accounts of Northern Trust Corporation (Corporation) and its wholly-owned subsidiary, The Northern Trust Company (Bank), and various other wholly-owned subsidiaries of the Corporation and Bank. Throughout the notes to the consolidated financial statements, the term “Northern Trust” refers to the Corporation and its subsidiaries. Intercompany balances and transactions have been eliminated in consolidation. The consolidated financial statements, as of and for the periods ended June 30, 2025 and 2024, have not been audited by the Corporation’s independent registered public accounting firm. In the opinion of management, all accounting entries and adjustments, including normal recurring accruals, necessary for a fair presentation of the financial position and the results of operations for the interim periods have been made. The accounting and financial reporting policies of Northern Trust conform to U.S. generally accepted accounting principles (GAAP) and reporting practices prescribed for the banking industry.

Recent Accounting Pronouncements

On January 1, 2025, Northern Trust adopted ASU No. 2023-08, “Intangibles—Goodwill and Other—Crypto Assets (Subtopic 350-60): Accounting for and Disclosure of Crypto Assets” (ASU 2023-08). ASU 2023-08 requires entities to subsequently measure certain crypto assets at fair value, with changes in fair value recorded in net income in each reporting period, and present crypto assets separately from other intangible assets on the face of the balance sheet and changes in fair value of crypto assets separately from changes in the carrying amount of other intangible assets on the statement of income. ASU 2023-08 also requires enhanced disclosures about in-scope crypto assets and respective activities. As Northern Trust does not hold crypto assets, upon adoption of ASU 2023-08, there was no impact on the consolidated balance sheets or consolidated statements of income.