Investment Securities - Unrealized Gross Losses and Fair Values of Securities in a Continuous Loss Position (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Securities in the available-for-sale portfolio in a continuous loss position
Number of individual securities in a continuous loss position | security	318	50
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses	$ (125,923)	$ (10,705)
12 Months or More Unrealized Losses	(31,373)	(25)
Total Unrealized Losses	(157,296)	(10,730)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value	6,044,029	1,068,883
12 Months or More Fair Value	497,202	6,190
Total Fair Value	$ 6,541,231	1,075,073
Credit losses		0
Investment securities comprised of collateralized loan obligations rated AA or better and obligations issued by local state and political subdivisions rated AA or better	2.00%
U.S. Treasury and government agency debt securities
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses	$ (3,355)	(61)
12 Months or More Unrealized Losses	(869)
Total Unrealized Losses	(4,224)	(61)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value	134,468	38,507
12 Months or More Fair Value	16,642
Total Fair Value	151,110	38,507
Residential - Government-sponsored enterprises
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses	(10,876)	(725)
12 Months or More Unrealized Losses	(1,543)
Total Unrealized Losses	(12,419)	(725)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value	1,230,104	64,987
12 Months or More Fair Value	32,415
Total Fair Value	1,262,519	64,987
Residential - Government agency
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses	(291)
Total Unrealized Losses	(291)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value	51,231
Total Fair Value	51,231
Commercial - Government agency
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses	(5,239)	(119)
12 Months or More Unrealized Losses	(1,282)
Total Unrealized Losses	(6,521)	(119)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value	186,024	32,346
12 Months or More Fair Value	26,063
Total Fair Value	212,087	32,346
Commercial - Government-sponsored enterprises
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses	(22,179)	(7,983)
12 Months or More Unrealized Losses	(26,535)
Total Unrealized Losses	(48,714)	(7,983)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value	744,819	427,759
12 Months or More Fair Value	397,123
Total Fair Value	1,141,942	427,759
Government agency
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses	(31,432)	(994)
12 Months or More Unrealized Losses		(25)
Total Unrealized Losses	(31,432)	(1,019)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value	1,441,848	209,124
12 Months or More Fair Value		6,190
Total Fair Value	1,441,848	215,314
Government-sponsored enterprises
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses	(52,551)	(823)
12 Months or More Unrealized Losses	(1,144)
Total Unrealized Losses	(53,695)	(823)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value	2,255,535	296,160
12 Months or More Fair Value	24,959
Total Fair Value	$ 2,280,494	$ 296,160