Securities (Schedule of Available-for-sale Debt Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Schedule of Available-for-sale Debt Securities
Total available-for-sale debt investment securities, Amortized Cost	$ 3,259,784	$ 2,806,900
Gross Unrealized Gains	32,319	5,714
Gross Unrealized Losses	(8,069)	(70,767)
Available-for-sale debt securities, Fair Value	3,284,034	2,741,847
U.S. Treasury securities
Schedule of Available-for-sale Debt Securities
Total available-for-sale debt investment securities, Amortized Cost	427,535	577,561
Gross Unrealized Gains	0	153
Gross Unrealized Losses	(1,422)	(12,899)
Available-for-sale debt securities, Fair Value	426,113	564,815
U.S. government agency and U.S. government sponsored enterprise debt securities
Schedule of Available-for-sale Debt Securities
Total available-for-sale debt investment securities, Amortized Cost	688,529	219,485
Gross Unrealized Gains	2,924	382
Gross Unrealized Losses	(85)	(2,694)
Available-for-sale debt securities, Fair Value	691,368	217,173
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Total available-for-sale debt investment securities, Amortized Cost	539,957	420,486
Gross Unrealized Gains	12,500	811
Gross Unrealized Losses	(2,664)	(12,694)
Available-for-sale debt securities, Fair Value	549,793	408,603
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Total available-for-sale debt investment securities, Amortized Cost	914,379	957,219
Gross Unrealized Gains	11,914	4,026
Gross Unrealized Losses	(906)	(14,552)
Available-for-sale debt securities, Fair Value	925,387	946,693
Municipal securities
Schedule of Available-for-sale Debt Securities
Total available-for-sale debt investment securities, Amortized Cost	76,948	82,965
Gross Unrealized Gains	1,218	87
Gross Unrealized Losses	(7)	(1,032)
Available-for-sale debt securities, Fair Value	78,159	82,020
Non-agency commercial mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Total available-for-sale debt investment securities, Amortized Cost	67,518	25,826
Gross Unrealized Gains	2,731	226
Gross Unrealized Losses	(6)	0
Available-for-sale debt securities, Fair Value	70,243	26,052
Non-agency residential mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Total available-for-sale debt investment securities, Amortized Cost	31,209	10,109
Gross Unrealized Gains	425	7
Gross Unrealized Losses	(139)	(185)
Available-for-sale debt securities, Fair Value	31,495	9,931
Corporate debt securities
Schedule of Available-for-sale Debt Securities
Total available-for-sale debt investment securities, Amortized Cost	11,250	11,250
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(228)	(381)
Available-for-sale debt securities, Fair Value	11,022	10,869
Foreign bonds
Schedule of Available-for-sale Debt Securities
Total available-for-sale debt investment securities, Amortized Cost	454,431	489,378
Gross Unrealized Gains	607	0
Gross Unrealized Losses	(1,859)	(26,330)
Available-for-sale debt securities, Fair Value	453,179	463,048
Asset-backed securities
Schedule of Available-for-sale Debt Securities
Total available-for-sale debt investment securities, Amortized Cost	48,028	12,621
Gross Unrealized Gains	0	22
Gross Unrealized Losses	(753)	0
Available-for-sale debt securities, Fair Value	$ 47,275	$ 12,643

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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