Securities (Schedule of Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	$ 3,320,648	$ 2,806,900
Gross Unrealized Gains	19,805	5,714
Gross Unrealized Losses	(23,239)	(70,767)
Available-for-sale debt securities, Fair Value	3,317,214	2,741,847
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	177,215	577,561
Gross Unrealized Gains	0	153
Gross Unrealized Losses	(793)	(12,899)
Available-for-sale debt securities, Fair Value	176,422	564,815
U.S. government agency and U.S. government sponsored enterprise debt securities
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	584,275	219,485
Gross Unrealized Gains	1,377	382
Gross Unrealized Losses	(4,407)	(2,694)
Available-for-sale debt securities, Fair Value	581,245	217,173
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	599,814	420,486
Gross Unrealized Gains	8,551	811
Gross Unrealized Losses	(4,894)	(12,694)
Available-for-sale debt securities, Fair Value	603,471	408,603
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	998,447	957,219
Gross Unrealized Gains	6,927	4,026
Gross Unrealized Losses	(1,477)	(14,552)
Available-for-sale debt securities, Fair Value	1,003,897	946,693
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	101,621	82,965
Gross Unrealized Gains	790	87
Gross Unrealized Losses	(109)	(1,032)
Available-for-sale debt securities, Fair Value	102,302	82,020
Non-agency commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	86,609	25,826
Gross Unrealized Gains	1,947	226
Gross Unrealized Losses	(6)	0
Available-for-sale debt securities, Fair Value	88,550	26,052
Non-agency residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	46,830	10,109
Gross Unrealized Gains	3	7
Gross Unrealized Losses	(285)	(185)
Available-for-sale debt securities, Fair Value	46,548	9,931
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	11,250	11,250
Gross Unrealized Gains	12	0
Gross Unrealized Losses	(113)	(381)
Available-for-sale debt securities, Fair Value	11,149	10,869
Foreign bonds
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	354,481	489,378
Gross Unrealized Gains	198	0
Gross Unrealized Losses	(507)	(26,330)
Available-for-sale debt securities, Fair Value	354,172	463,048
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	66,106	12,621
Gross Unrealized Gains	0	22
Gross Unrealized Losses	(1,354)	0
Available-for-sale debt securities, Fair Value	64,752	$ 12,643
CLOs
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities, Amortized Cost	294,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(9,294)
Available-for-sale debt securities, Fair Value	$ 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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