Regulatory Capital and Restrictions - Schedule of Information on Capital Ratios (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2025	Jun. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Actual, CET1 Risk-Based Capital		$ 6,406,260	$ 6,318,876
Actual, Tier 1 Risk-Based Capital		6,690,239	6,602,855
Actual, Total Risk-Based Capital		7,927,728	7,800,717
Actual, Tier 1 Leverage Capital		$ 6,690,239	$ 6,602,855
Ratio, CET1 Risk-Based Capital		0.1135	0.1154
Actual, Ratio, Tier 1 Risk-Based Capital		0.1186	0.1206
Ratio, Total Risk-Based Capital		0.1405	0.1424
Actual, Ratio, Tier 1 Leverage Capital		0.0857	0.0870
Minimum Requirement, CET1 Risk-Based Capital		$ 2,539,270	$ 2,464,542
Minimum Requirement, Tier 1 Risk-Based Capital		3,385,694	3,286,057
Minimum Requirement, Total Risk-Based Capital		4,514,258	4,381,409
Minimum Requirement, Tier 1, Leverage Capital		$ 3,121,275	$ 3,034,369
Minimum Requirement, Ratio, Tier 1 Risk-Based Capital		0.060	0.060
Minimum Requirement, Ratio, Total Risk-Based Capital		0.080	0.080
Minimum Requirement, Ratio, Tier 1 Leverage Capital		0.040	0.040
Well Capitalized, CET1 Risk-Based Capital		$ 3,667,835	$ 3,559,895
Well Capitalized, Tier 1 Risk-Based Capital		4,514,258	4,381,409
Well Capitalized, Total Risk-Based Capital		5,642,823	5,476,761
Well Capitalized, Tier 1 Leverage Capital		$ 3,901,593	$ 3,792,961
Well Capitalized, Ratio, Tier 1 Risk-Based Capital		0.080	0.080
Well Capitalized, Ratio, Total Risk-Based Capital		0.100	0.100
Well Capitalized, Ratio, Tier 1 Leverage Capital		0.050	0.050
Transition regulatory capital percentage	25.00%
Subsidiaries
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Actual, CET1 Risk-Based Capital		$ 7,076,737	$ 6,847,474
Actual, Tier 1 Risk-Based Capital		7,076,737	6,847,474
Actual, Total Risk-Based Capital		7,782,131	7,512,143
Actual, Tier 1 Leverage Capital		$ 7,076,737	$ 6,847,474
Ratio, CET1 Risk-Based Capital		0.1255	0.1253
Actual, Ratio, Tier 1 Risk-Based Capital		0.1255	0.1253
Ratio, Total Risk-Based Capital		0.1380	0.1374
Actual, Ratio, Tier 1 Leverage Capital		0.0908	0.0904
Minimum Requirement, CET1 Risk-Based Capital		$ 2,538,304	$ 2,460,031
Minimum Requirement, Tier 1 Risk-Based Capital		3,384,405	3,280,042
Minimum Requirement, Total Risk-Based Capital		4,512,540	4,373,389
Minimum Requirement, Tier 1, Leverage Capital		$ 3,118,568	$ 3,031,190
Minimum Requirement, Ratio, Tier 1 Risk-Based Capital		0.060	0.060
Minimum Requirement, Ratio, Total Risk-Based Capital		0.080	0.080
Minimum Requirement, Ratio, Tier 1 Leverage Capital		0.040	0.040
Well Capitalized, CET1 Risk-Based Capital		$ 3,666,439	$ 3,553,378
Well Capitalized, Tier 1 Risk-Based Capital		4,512,540	4,373,389
Well Capitalized, Total Risk-Based Capital		5,640,675	5,466,736
Well Capitalized, Tier 1 Leverage Capital		$ 3,898,210	$ 3,788,988
Well Capitalized, Ratio, Tier 1 Risk-Based Capital		0.080	0.080
Well Capitalized, Ratio, Total Risk-Based Capital		0.100	0.100
Well Capitalized, Ratio, Tier 1 Leverage Capital		0.050	0.050
Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Ratio, CET1 Risk-Based Capital		0.045	0.045
Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets \| Subsidiaries
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Ratio, CET1 Risk-Based Capital		0.045	0.045
Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Ratio, CET1 Risk-Based Capital		0.065	0.065
Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets \| Subsidiaries
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Ratio, CET1 Risk-Based Capital		0.065	0.065

Amount of total capital as defined by regulatory framework.

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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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