Stock Based Compensation - Summary of Status of United's Nonvested Stock Option Awards (Detail)	6 Months Ended
Jun. 30, 2026 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares, Granted	0
Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares, Nonvested, Beginning balance	595,485
Shares, Granted	226,556
Shares, Vested	(157,695)
Shares, Forfeited or expired	(28,880)
Shares, Nonvested, Ending balance	635,466
Weighted-Average Grant Date Fair Value Per Share, Nonvested Beginning balance \| $ / shares	$ 35.28
Weighted-Average Grant Date Fair Value Per Share, Granted \| $ / shares	47.83
Weighted-Average Grant Date Fair Value Per Share, Vested \| $ / shares	38.24
Weighted-Average Grant Date Fair Value Per Share, Forfeited or expired \| $ / shares	39.89
Weighted-Average Grant Date Fair Value Per Share, Nonvested Ending balance \| $ / shares	$ 38.81

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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