Securities (Schedule of Available-for-sale Debt Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule of Available-for-sale Debt Securities
Amortized Cost	$ 9,783,180	$ 5,470,523
Gross Unrealized Gains	63,504	96,596
Gross Unrealized Losses	(133,678)	(22,461)
Fair Value	9,713,006	5,544,658
U.S. Treasury securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	950,260	50,310
Gross Unrealized Gains	233	451
Gross Unrealized Losses	(8,769)	0
Fair Value	941,724	50,761
U.S. government agency and U.S. government-sponsored enterprise debt securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	1,386,236	806,814
Gross Unrealized Gains	4,401	8,765
Gross Unrealized Losses	(27,528)	(1,260)
Fair Value	1,363,109	814,319
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	1,277,989	1,125,174
Gross Unrealized Gains	19,063	34,306
Gross Unrealized Losses	(22,585)	(5,710)
Fair Value	1,274,467	1,153,770
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	2,814,111	1,634,553
Gross Unrealized Gains	13,875	27,952
Gross Unrealized Losses	(36,922)	(1,611)
Fair Value	2,791,064	1,660,894
Municipal securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	500,907	382,573
Gross Unrealized Gains	8,194	13,588
Gross Unrealized Losses	(7,612)	(88)
Fair Value	501,489	396,073
Non-agency commercial mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	463,358	234,965
Gross Unrealized Gains	4,704	6,107
Gross Unrealized Losses	(3,292)	(1,230)
Fair Value	464,770	239,842
Non-agency residential mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	902,002	288,520
Gross Unrealized Gains	2,490	1,761
Gross Unrealized Losses	(3,236)	(506)
Fair Value	901,256	289,775
Corporate debt securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	626,531	406,323
Gross Unrealized Gains	9,445	3,493
Gross Unrealized Losses	(17,305)	(3,848)
Fair Value	618,671	405,968
Foreign government bonds
Schedule of Available-for-sale Debt Securities
Amortized Cost	258,119	183,828
Gross Unrealized Gains	657	163
Gross Unrealized Losses	(3,928)	(1,460)
Fair Value	254,848	182,531
Asset-backed securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	76,417	63,463
Gross Unrealized Gains	437	10
Gross Unrealized Losses	(55)	(242)
Fair Value	76,799	63,231
Collateralized loan obligations (“CLOs”)
Schedule of Available-for-sale Debt Securities
Amortized Cost	527,250	294,000
Gross Unrealized Gains	5	0
Gross Unrealized Losses	(2,446)	(6,506)
Fair Value	$ 524,809	$ 287,494

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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Amount, before tax, of unrealized loss 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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