Investment Securities - Gross unrealized losses and fair value (Details) $ in Thousands	Sep. 30, 2022 USD ($) security	Dec. 31, 2021 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Number of securities \| security	262	239
Less than 12 months, estimated fair value	$ 1,182,005	$ 1,891,310
Less than 12 months, unrealized losses	(140,542)	(24,285)
12 months or greater, estimated fair value	458,292	177,038
12 months or greater, unrealized losses	(83,594)	(5,322)
Estimated fair value	1,640,297	2,068,348
Unrealized losses	$ (224,136)	$ (29,607)
U.S. treasury bonds
Debt Securities, Available-for-sale [Line Items]
Number of securities \| security	2	1
Less than 12 months, estimated fair value	$ 46,048	$ 24,593
Less than 12 months, unrealized losses	(3,719)	(257)
12 months or greater, estimated fair value	0	0
12 months or greater, unrealized losses	0	0
Estimated fair value	46,048	24,593
Unrealized losses	$ (3,719)	$ (257)
U. S. agency securities
Debt Securities, Available-for-sale [Line Items]
Number of securities \| security	84	64
Less than 12 months, estimated fair value	$ 450,079	$ 452,966
Less than 12 months, unrealized losses	(49,232)	(6,256)
12 months or greater, estimated fair value	212,988	68,977
12 months or greater, unrealized losses	(33,452)	(1,366)
Estimated fair value	663,067	521,943
Unrealized losses	$ (82,684)	$ (7,622)
Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Number of securities \| security	159	153
Less than 12 months, estimated fair value	$ 581,381	$ 1,327,519
Less than 12 months, unrealized losses	(80,300)	(16,841)
12 months or greater, estimated fair value	245,304	108,061
12 months or greater, unrealized losses	(50,142)	(3,956)
Estimated fair value	826,685	1,435,580
Unrealized losses	$ (130,442)	$ (20,797)
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Number of securities \| security	14
Less than 12 months, estimated fair value	$ 94,172
Less than 12 months, unrealized losses	(6,106)
12 months or greater, estimated fair value	0
12 months or greater, unrealized losses	0
Estimated fair value	94,172
Unrealized losses	$ (6,106)
Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Number of securities \| security	2	8
Less than 12 months, estimated fair value	$ 8,463	$ 20,181
Less than 12 months, unrealized losses	(1,047)	(347)
12 months or greater, estimated fair value	0	0
12 months or greater, unrealized losses	0	0
Estimated fair value	8,463	20,181
Unrealized losses	$ (1,047)	$ (347)
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Number of securities \| security	1	13
Less than 12 months, estimated fair value	$ 1,862	$ 66,051
Less than 12 months, unrealized losses	(138)	(584)
12 months or greater, estimated fair value	0	0
12 months or greater, unrealized losses	0	0
Estimated fair value	1,862	66,051
Unrealized losses	$ (138)	$ (584)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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