Segment Information (Summary of Certain Operating Information For Reportable Segments) (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
Segment Reporting Information [Line Items]
Net interest income	$ 254,088	$ 247,563	$ 238,170	$ 225,082	$ 219,099	$ 215,988	$ 204,409	$ 192,580	$ 964,903	$ 832,076	$ 722,193
Provision for credit losses	10,401	11,042	5,043	8,346	7,772	7,896	8,891	5,209	34,832	29,768	34,084
Non-interest income									356,150	319,506	325,430
Non-interest expense	211,333	213,637	206,769	194,349	196,580	183,575	183,544	168,118	826,088	731,817	681,685
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
Total assets at end of year	31,244,849				27,915,970				31,244,849	27,915,970	25,668,553
Operating Segments
Segment Reporting Information [Line Items]
Net interest income									946,274	814,720	705,706
Provision for credit losses									34,832	29,768	34,084
Non-interest income									396,462	356,071	358,598
Non-interest expense									847,771	751,026	698,366
Income tax expense									116,967	132,315	124,979
Net income									343,166	257,682	206,875
Total assets at end of year	31,244,849				27,915,970				31,244,849	27,915,970	25,668,553
Operating Segments | Community Banking
Segment Reporting Information [Line Items]
Net interest income									791,838	677,481	588,847
Provision for credit losses									28,586	27,059	30,862
Non-interest income									238,668	211,354	230,414
Non-interest expense									681,749	599,455	556,798
Income tax expense									79,361	87,486	86,933
Net income									240,810	174,835	144,668
Total assets at end of year	25,438,454				22,781,923				25,438,454	22,781,923	21,172,080
Operating Segments | Specialty Finance
Segment Reporting Information [Line Items]
Net interest income									136,981	118,320	98,248
Provision for credit losses									6,246	2,709	3,222
Non-interest income									65,898	60,405	49,706
Non-interest expense									84,248	74,559	66,460
Income tax expense									30,325	35,775	29,512
Net income									82,060	65,682	48,760
Total assets at end of year	5,073,011				4,515,766				5,073,011	4,515,766	3,884,373
Operating Segments | Wealth Management
Segment Reporting Information [Line Items]
Net interest income									17,455	18,919	18,611
Provision for credit losses									0	0	0
Non-interest income									91,896	84,312	78,478
Non-interest expense									81,774	77,012	75,108
Income tax expense									7,281	9,054	8,534
Net income									20,296	17,165	13,447
Total assets at end of year	733,384				618,281				733,384	618,281	612,100
Intersegment Eliminations
Segment Reporting Information [Line Items]
Net interest income									18,629	17,356	16,487
Provision for credit losses									0	0	0
Non-interest income									(40,312)	(36,565)	(33,168)
Non-interest expense									(21,683)	(19,209)	(16,681)
Income tax expense									0	0	0
Net income									0	0	0
Total assets at end of year	$ 0				$ 0				$ 0	$ 0	$ 0