Shareholders' Equity (Reclassification from Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
(Losses) gains on investment securities, net	$ (2,649)	$ 90	$ 12	$ (351)	$ 14	$ 39	$ 47	$ (55)	$ (2,898)	$ 45	$ 7,645
Interest on deposits									166,553	83,326	58,409
Interest on other borrowings									8,599	5,370	4,355
Interest on junior subordinated debentures									11,222	9,782	9,503
Income before taxes	107,662	122,814	121,591	108,066	95,785	104,248	101,946	88,018	460,133	389,997	331,854
Income tax expense	28,005	30,866	32,011	26,085	27,004	38,622	37,049	29,640	116,967	132,315	124,979
Net income	$ 79,657	$ 91,948	$ 89,580	$ 81,981	$ 68,781	$ 65,626	$ 64,897	$ 58,378	343,166	257,682	$ 206,875
Reclassification out of Accumulated Other Comprehensive Income | Accumulated unrealized losses on available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
(Losses) gains on investment securities, net									33	45
Income before taxes									33	45
Income tax expense									9	18
Net income									24	27
Reclassification out of Accumulated Other Comprehensive Income | Accumulated unrealized losses on derivative instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest on deposits									(7,549)	(1,085)
Interest on other borrowings									236	0
Interest on junior subordinated debentures									0	1,066
Income before taxes									7,313	19
Income tax expense									1,965	8
Net income									$ 5,348	$ 11