Summary of Significant Accounting Policies (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2018	Jan. 01, 2020	Dec. 31, 2019	Jan. 01, 2019	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash on hand or on deposit required	$ 42,000			$ 918,000
Cash collateral on deposit	74,000			37,500
Foreclosed assets	850			1,100
Cumulative effect of accounting change		$ (14,672)		(29,252)			$ (2,285)
Operating Lease, Right-of-Use Asset	$ 292,087			297,736	$ 170,500
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Range of change in fair value of derivative hedging instrument to be considered highly effective	80.00%
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Range of change in fair value of derivative hedging instrument to be considered highly effective	125.00%
Other Liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability	$ 323,044			323,700	174,400
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change		(14,672)	$ (29,300)	$ (29,252)	$ (14,700)	$ (2,300)	$ (2,285)
Reclassification of certain income tax effects related to the change in the U.S. statutory federal income tax rate under the Tax Cuts and Jobs Act		(9,535)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of certain income tax effects related to the change in the U.S. statutory federal income tax rate under the Tax Cuts and Jobs Act		$ 9,535