Stockholders' Equity (Changes in Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 8,902
Unrealized gains on investment securities available for sale:
Net unrealized holding gain (loss) arising during the period, Before Tax	$ 11,372	$ (24,690)	$ 72,519	(79,697)
Amounts reclassified to gain on investment securities available for sale, net, Before Tax	(3,426)	(520)	(11,657)	(4,047)
Net change in unrealized gains on securities available for sale, Before Tax	7,946	(25,210)	60,862	(83,744)
Net unrealized holding gain (loss) arising during the period, Tax Effect	(3,014)	6,543	(19,218)	21,120
Amounts reclassified to gain on investment securities available for sale, net, Tax Effect	908	138	3,089	1,073
Net change in unrealized gains on securities available for sale, Tax Effect	(2,106)	6,681	(16,129)	22,193
Net unrealized holding gain (loss) arising during the period, Net of Tax	8,358	(18,147)	53,301	(58,577)
Amounts reclassified to gain on investment securities available for sale, net, Net of Tax	(2,518)	(382)	(8,568)	(2,974)
Net change in unrealized gain on securities available for sale	5,840	(18,529)	44,733	(61,551)
Unrealized losses on derivative instruments:
Net unrealized holding gain (loss) arising during the period, Before Tax	(22,822)	14,335	(101,588)	54,660
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	(509)	(1,050)	(4,920)	(839)
Net change in unrealized losses on derivative instruments, Before Tax	(23,331)	13,285	(106,508)	53,821
Net unrealized holding gain (loss) arising during the period, Tax Effect	6,048	(3,799)	26,921	(14,485)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	135	278	1,304	222
Net change in unrealized losses on derivative instruments, Tax Effect	6,183	(3,521)	28,225	(14,263)
Net unrealized holding gain (loss) arising during the period, Net of Tax	(16,774)	10,536	(74,667)	40,175
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(374)	(772)	(3,616)	(617)
Net change in unrealized loss on derivative instruments	(17,148)	9,764	(78,283)	39,558
Other comprehensive income (loss), Before Tax	(15,385)	(11,925)	(45,646)	(29,923)
Other comprehensive income (loss), Tax Effect	4,077	3,160	12,096	7,930
Other comprehensive income (loss)	$ (11,308)	$ (8,765)	$ (33,550)	$ (21,993)