Securities (Schedule of Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 5,470,523	$ 3,320,648
Gross Unrealized Gains	96,596	19,805
Gross Unrealized Losses	(22,461)	(23,239)
Fair Value	5,544,658	3,317,214
Debt securities available for sale
Debt Securities, Available-for-sale [Line Items]
Accrued interest receivables	22,300	11,100
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	50,310	177,215
Gross Unrealized Gains	451	0
Gross Unrealized Losses	0	(793)
Fair Value	50,761	176,422
U.S. government agency and U.S. government-sponsored enterprise debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	806,814	584,275
Gross Unrealized Gains	8,765	1,377
Gross Unrealized Losses	(1,260)	(4,407)
Fair Value	814,319	581,245
US government agencies And U.S. government-sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,125,174	599,814
Gross Unrealized Gains	34,306	8,551
Gross Unrealized Losses	(5,710)	(4,894)
Fair Value	1,153,770	603,471
US government agencies And U.S. government-sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,634,553	998,447
Gross Unrealized Gains	27,952	6,927
Gross Unrealized Losses	(1,611)	(1,477)
Fair Value	1,660,894	1,003,897
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	382,573	101,621
Gross Unrealized Gains	13,588	790
Gross Unrealized Losses	(88)	(109)
Fair Value	396,073	102,302
Non-agency commercial mortgage-backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	234,965	86,609
Gross Unrealized Gains	6,107	1,947
Gross Unrealized Losses	(1,230)	(6)
Fair Value	239,842	88,550
Non-agency residential mortgage-backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	288,520	46,830
Gross Unrealized Gains	1,761	3
Gross Unrealized Losses	(506)	(285)
Fair Value	289,775	46,548
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	406,323	11,250
Gross Unrealized Gains	3,493	12
Gross Unrealized Losses	(3,848)	(113)
Fair Value	405,968	11,149
Foreign government bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	183,828	354,481
Gross Unrealized Gains	163	198
Gross Unrealized Losses	(1,460)	(507)
Fair Value	182,531	354,172
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	63,463	66,106
Gross Unrealized Gains	10	0
Gross Unrealized Losses	(242)	(1,354)
Fair Value	63,231	64,752
CLOs
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	294,000	294,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(6,506)	(9,294)
Fair Value	$ 287,494	$ 284,706

Interest, dividends, rents, ancillary and other revenues earned but not yet received by the entity on its investments.

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