Debt Securities - Debt Securities in an Unrealized Loss Position (Details) $ in Thousands	Jun. 30, 2022 USD ($) security	Dec. 31, 2021 USD ($) security
Available-for-sale
Number of available-for-sale securities | security	823	263
Less than 12 months, fair value	$ 4,932,966	$ 7,231,306
Less than 12 months, unrealized loss	(354,315)	(67,190)
12 months or more, fair value	880,773	187,060
12 months or more, unrealized loss	(77,992)	(5,501)
Total, fair value	5,813,739	7,418,366
Total, unrealized loss	$ (432,307)	$ (72,691)
U.S. government and federal agency
Available-for-sale
Number of available-for-sale securities | security	46	50
Less than 12 months, fair value	$ 447,250	$ 1,329,399
Less than 12 months, unrealized loss	(31,667)	(9,344)
12 months or more, fair value	4,071	5,457
12 months or more, unrealized loss	(340)	(252)
Total, fair value	451,321	1,334,856
Total, unrealized loss	$ (32,007)	$ (9,596)
U.S. government sponsored enterprises
Available-for-sale
Number of available-for-sale securities | security	15	11
Less than 12 months, fair value	$ 297,813	$ 239,928
Less than 12 months, unrealized loss	(21,695)	(996)
12 months or more, fair value	0	0
12 months or more, unrealized loss	0	0
Total, fair value	297,813	239,928
Total, unrealized loss	$ (21,695)	$ (996)
State and local governments
Available-for-sale
Number of available-for-sale securities | security	193	10
Less than 12 months, fair value	$ 217,517	$ 11,080
Less than 12 months, unrealized loss	(5,437)	(83)
12 months or more, fair value	1,579	1,760
12 months or more, unrealized loss	(213)	(40)
Total, fair value	219,096	12,840
Total, unrealized loss	$ (5,650)	$ (123)
Corporate bonds
Available-for-sale
Number of available-for-sale securities | security	11	3
Less than 12 months, fair value	$ 35,458	$ 12,483
Less than 12 months, unrealized loss	(482)	(17)
12 months or more, fair value	0	0
12 months or more, unrealized loss	0	0
Total, fair value	35,458	12,483
Total, unrealized loss	$ (482)	$ (17)
Residential mortgage-backed securities
Available-for-sale
Number of available-for-sale securities | security	417	151
Less than 12 months, fair value	$ 2,952,869	$ 5,335,632
Less than 12 months, unrealized loss	(245,705)	(53,434)
12 months or more, fair value	747,910	53,045
12 months or more, unrealized loss	(64,412)	(832)
Total, fair value	3,700,779	5,388,677
Total, unrealized loss	$ (310,117)	$ (54,266)
Commercial mortgage-backed securities
Available-for-sale
Number of available-for-sale securities | security	141	38
Less than 12 months, fair value	$ 982,059	$ 302,784
Less than 12 months, unrealized loss	(49,329)	(3,316)
12 months or more, fair value	127,213	126,798
12 months or more, unrealized loss	(13,027)	(4,377)
Total, fair value	1,109,272	429,582
Total, unrealized loss	$ (62,356)	$ (7,693)