Stockholders' Equity (Changes in Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unrealized gains on investment securities available for sale:
Net unrealized holding gain (loss) arising during the period, Before Tax	$ (77,607)	$ 49,131	$ 23,588
Amounts reclassified to gain on investment securities available for sale, net, Before Tax	(6,103)	(33,466)	(14,461)
Net change in unrealized gains on securities available for sale, Before Tax	(83,710)	15,665	9,127
Net unrealized holding gain (loss) arising during the period, Tax Effect	20,566	(19,407)	(9,317)
Amounts reclassified to gain on investment securities available for sale, net, Tax Effect	1,617	13,219	5,712
Net change in unrealized gains on securities available for sale, Tax Effect	22,183	(6,188)	(3,605)
Net unrealized holding gain (loss) arising during the period, Net of Tax	(57,041)	29,724	14,271
Amounts reclassified to gain on investment securities available for sale, net, Net of Tax	(4,486)	(20,247)	(8,749)
Net change in unrealized gain on securities available for sale	(61,527)	9,477	5,522
Unrealized losses on derivative instruments:
Net unrealized holding gain (loss) arising during the period, Before Tax	5,416	(2,577)	6,225
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	(1,999)	9,621	16,161
Net change in unrealized losses on derivative instruments, Before Tax	3,417	7,044	22,386
Net unrealized holding gain (loss) arising during the period, Tax Effect	(1,435)	1,018	(2,459)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	530	(3,800)	(6,384)
Net change in unrealized losses on derivative instruments, Tax Effect	(905)	(2,782)	(8,843)
Net unrealized holding gain (loss) arising during the period, Net of Tax	3,981	(1,559)	3,766
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(1,469)	5,821	9,777
Net change in unrealized gains on derivative instruments	2,512	4,262	13,543
Other comprehensive income (loss), Before Tax	(80,293)	22,709	31,513
Other comprehensive income (loss), Tax Effect	21,278	(8,970)	(12,448)
Other comprehensive income (loss)	$ (59,015)	$ 13,739	$ 19,065