Income Taxes (Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Taxes computed at statutory rate, amount	$ 119,292	$ (26,196)	$ 82,475
State income taxes, net of federal income tax benefit, amount	9,048	(1,269)	7,204
Tax-exempt interest, amount	(9,100)	(10,444)	(10,435)
Life insurance contracts, amount	(2,653)	(4,857)	(3,901)
Tax credits, amount	(7,889)	(8,072)	(10,293)
Employee share-based compensation, amount	(1,671)	1,351	(842)
FDIC assessment disallowance, amount	1,609	2,094	1,895
Net operating loss carryback under CARES act, amount	(4,948)	(30,167)
Other, net, amount	1,153	(2,011)	(744)
Total expense (benefit) included in net income	$ 104,841	$ (79,571)	$ 65,359
Taxes computed at statutory rate	21.00%	21.00%	21.00%	35.00%
State income taxes, net of federal income tax benefit	1.60%	1.00%	1.80%
Tax-exempt interest	(1.60%)	8.40%	(2.70%)
Life insurance contracts	(0.50%)	3.90%	(1.00%)
Tax credits	(1.40%)	6.50%	(2.60%)
Employee share-based compensation	(0.30%)	(1.10%)	(0.20%)
FDIC assessment disallowance	0.30%	(1.70%)	0.50%
Net operating loss carryback under CARES act	(0.90%)	24.20%
Other, net	0.30%	1.60%	(0.20%)
Income tax expense (benefit)	18.50%	63.80%	16.60%