Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 463,215	$ (45,174)	$ 327,380
Other comprehensive income (loss) before income taxes:
Net change in unrealized gain/loss on available for sale securities and cash flow hedges	(211,580)	224,337	143,922
Reclassification of net gains (losses) realized and included in earnings	(15,485)	(10,983)	13,429
Valuation adjustments for employee benefit plans	(6,735)	(37,451)	2,398
Voluntary Early Retirement Incentive Program (VERIP) and curtailment	59,606
Amortization of unrealized net loss on securities transferred to held to maturity	(158)	(470)	3,153
Other comprehensive income (loss) before income taxes	(174,352)	175,433	162,902
Income tax expense (benefit)	(40,348)	40,640	36,917
Other comprehensive income (loss) net of income taxes	(134,004)	134,793	125,985
Comprehensive income	$ 329,211	$ 89,619	$ 453,365