Securities (Schedule of Available-for-sale Debt Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Debt Securities
Amortized Cost	$ 7,904,546	$ 5,470,523
Gross Unrealized Gains	57,453	96,596
Gross Unrealized Losses	(172,786)	(22,461)
Fair Value	7,789,213	5,544,658
U.S. Treasury securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	841,711	50,310
Gross Unrealized Gains	328	451
Gross Unrealized Losses	(15,697)	0
Fair Value	826,342	50,761
U.S. government agency and U.S. government-sponsored enterprise debt securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	1,236,446	806,814
Gross Unrealized Gains	5,145	8,765
Gross Unrealized Losses	(47,586)	(1,260)
Fair Value	1,194,005	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	1,178,238	1,125,174
Gross Unrealized Gains	16,407	34,306
Gross Unrealized Losses	(25,254)	(5,710)
Fair Value	1,169,391	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	2,271,645	1,634,553
Gross Unrealized Gains	17,026	27,952
Gross Unrealized Losses	(41,265)	(1,611)
Fair Value	2,247,406	1,660,894
Municipal securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	417,676	382,573
Gross Unrealized Gains	7,348	13,588
Gross Unrealized Losses	(4,959)	(88)
Fair Value	420,065	396,073
Non-agency commercial mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	281,099	234,965
Gross Unrealized Gains	4,311	6,107
Gross Unrealized Losses	(4,383)	(1,230)
Fair Value	281,027	239,842
Non-agency residential mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	525,560	288,520
Gross Unrealized Gains	1,599	1,761
Gross Unrealized Losses	(3,659)	(506)
Fair Value	523,500	289,775
Corporate debt securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	517,309	406,323
Gross Unrealized Gains	4,677	3,493
Gross Unrealized Losses	(25,343)	(3,848)
Fair Value	496,643	405,968
Foreign government bonds
Schedule of Available-for-sale Debt Securities
Amortized Cost	278,100	183,828
Gross Unrealized Gains	320	163
Gross Unrealized Losses	(2,092)	(1,460)
Fair Value	276,328	182,531
Asset-backed securities
Schedule of Available-for-sale Debt Securities
Amortized Cost	62,762	63,463
Gross Unrealized Gains	292	10
Gross Unrealized Losses	(14)	(242)
Fair Value	63,040	63,231
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	(2,534)	(6,506)
Fair Value	$ 291,466	$ 287,494