Securities (Schedule of Available-for-sale Debt Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Available-for-sale Debt Securities
Amortized Cost	$ 4,471,694	$ 3,320,648
Gross Unrealized Gains	92,913	19,805
Gross Unrealized Losses	(25,447)	(23,239)
AFS debt securities, Fair Value	4,539,160	3,317,214
U.S. Treasury securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	50,410	177,215
Gross Unrealized Gains	588	0
Gross Unrealized Losses	0	(793)
AFS debt securities, Fair Value	50,998	176,422
U.S. government agency and U.S. government-sponsored enterprise debt securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	718,907	584,275
Gross Unrealized Gains	10,565	1,377
Gross Unrealized Losses	(2,410)	(4,407)
AFS debt securities, Fair Value	727,062	581,245
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	937,078	599,814
Gross Unrealized Gains	34,292	8,551
Gross Unrealized Losses	(4,261)	(4,894)
AFS debt securities, Fair Value	967,109	603,471
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	1,206,488	998,447
Gross Unrealized Gains	32,578	6,927
Gross Unrealized Losses	(1,057)	(1,477)
AFS debt securities, Fair Value	1,238,009	1,003,897
Municipal securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	327,422	101,621
Gross Unrealized Gains	7,199	790
Gross Unrealized Losses	(1,346)	(109)
AFS debt securities, Fair Value	333,275	102,302
Non-agency commercial mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	210,343	86,609
Gross Unrealized Gains	5,556	1,947
Gross Unrealized Losses	(1,223)	(6)
AFS debt securities, Fair Value	214,676	88,550
Non-agency residential mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	277,306	46,830
Gross Unrealized Gains	782	3
Gross Unrealized Losses	(475)	(285)
AFS debt securities, Fair Value	277,613	46,548
Corporate debt securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	251,253	11,250
Gross Unrealized Gains	1,327	12
Gross Unrealized Losses	(1,403)	(113)
AFS debt securities, Fair Value	251,177	11,149
Foreign government bonds
Schedule of Available-for-sale Debt Securities
Amortized Cost	134,179	354,481
Gross Unrealized Gains	26	198
Gross Unrealized Losses	(1,534)	(507)
AFS debt securities, Fair Value	132,671	354,172
Asset-backed securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	64,308	66,106
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,160)	(1,354)
AFS debt securities, Fair Value	63,148	64,752
Collateralized loan obligations (“CLOs”)
Schedule of Available-for-sale Debt Securities
Amortized Cost	294,000	294,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(10,578)	(9,294)
AFS debt securities, Fair Value	$ 283,422	$ 284,706

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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