Investment Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Available for sale debt securities
Amortized Cost	$ 8,733,170	$ 8,560,733
Unrealized Gains	568	24,595
Unrealized Losses	(671,354)	(157,296)
Total available-for-sale securities, Fair value,	8,062,384	8,428,032
Available-for-sale investment securities
Accrued interest receivable related to available-for-sale investment securities	15,000	14,100
Collateralized Loan Obligations
Available for sale debt securities
Amortized Cost	221,607	105,245
Unrealized Gains	25	2
Unrealized Losses	(748)
Total available-for-sale securities, Fair value,	220,884	105,247
U.S. Treasury and government agency debt securities
Available for sale debt securities
Amortized Cost	213,572	196,662
Unrealized Gains		125
Unrealized Losses	(14,028)	(4,224)
Total available-for-sale securities, Fair value,	199,544	192,563
Residential - Government agency
Available for sale debt securities
Amortized Cost	128,080	135,764
Unrealized Gains		1,791
Unrealized Losses	(5,115)	(291)
Total available-for-sale securities, Fair value,	122,965	137,264
Residential - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	1,450,070	1,496,605
Unrealized Gains	428	6,914
Unrealized Losses	(88,153)	(12,419)
Total available-for-sale securities, Fair value,	1,362,345	1,491,100
Commercial - Government agency
Available for sale debt securities
Amortized Cost	358,910	392,443
Unrealized Gains	53	1,741
Unrealized Losses	(25,874)	(6,521)
Total available-for-sale securities, Fair value,	333,089	387,663
Commercial - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	1,426,831	1,415,511
Unrealized Gains		2,646
Unrealized Losses	(176,997)	(48,714)
Total available-for-sale securities, Fair value,	1,249,834	1,369,443
Government agency
Available for sale debt securities
Amortized Cost	2,153,236	2,103,187
Unrealized Gains	59	7,768
Unrealized Losses	(143,514)	(31,432)
Total available-for-sale securities, Fair value,	2,009,781	2,079,523
Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	2,719,829	2,671,131
Unrealized Gains	3	3,608
Unrealized Losses	(210,125)	(53,695)
Total available-for-sale securities, Fair value,	2,509,707	2,621,044
Debt securities issued by states and political subdivisions
Available for sale debt securities
Amortized Cost	61,035	44,185
Unrealized Losses	(6,800)
Total available-for-sale securities, Fair value,	$ 54,235	$ 44,185

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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