Segment Information (Summary of Certain Operating Information For Reportable Segments) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 261,879	$ 264,852	$ 266,202	$ 261,986	$ 254,088	$ 247,563	$ 238,170	$ 225,082	$ 1,054,919	$ 964,903	$ 832,076
Provision for credit losses	7,826	10,834	24,580	10,624	10,401	11,042	5,043	8,346	53,864	34,832	29,768
Non-interest income									407,172	356,150	319,506
Non-interest expense	249,591	234,554	229,607	214,374	211,333	213,637	206,769	194,349	928,126	826,088	731,817
Income tax expense	30,718	35,480	28,707	29,499	28,005	30,866	32,011	26,085	124,404	116,967	132,315
Net income	85,964	$ 99,121	$ 81,466	$ 89,146	79,657	$ 91,948	$ 89,580	$ 81,981	355,697	343,166	257,682
Total assets at end of year	36,620,583				31,244,849				36,620,583	31,244,849	27,915,970
Operating Segments
Segment Reporting Information [Line Items]
Net interest income									1,033,439	946,274	814,720
Provision for credit losses									53,864	34,832	29,768
Non-interest income									454,240	396,462	356,071
Non-interest expense									953,714	847,771	751,026
Income tax expense									124,404	116,967	132,315
Net income									355,697	343,166	257,682
Total assets at end of year	36,620,583				31,244,849				36,620,583	31,244,849	27,915,970
Operating Segments | Community Banking
Segment Reporting Information [Line Items]
Net interest income									841,601	791,838	677,481
Provision for credit losses									47,914	28,586	27,059
Non-interest income									274,652	238,668	211,354
Non-interest expense									747,202	681,749	599,455
Income tax expense									82,639	79,361	87,486
Net income									238,498	240,810	174,835
Total assets at end of year	29,583,112				25,438,454				29,583,112	25,438,454	22,781,923
Operating Segments | Specialty Finance
Segment Reporting Information [Line Items]
Net interest income									161,720	136,981	118,320
Provision for credit losses									5,950	6,246	2,709
Non-interest income									79,467	65,898	60,405
Non-interest expense									111,377	84,248	74,559
Income tax expense									34,424	30,325	35,775
Net income									89,436	82,060	65,682
Total assets at end of year	5,916,835				5,073,011				5,916,835	5,073,011	4,515,766
Operating Segments | Wealth Management
Segment Reporting Information [Line Items]
Net interest income									30,118	17,455	18,919
Provision for credit losses									0	0	0
Non-interest income									100,121	91,896	84,312
Non-interest expense									95,135	81,774	77,012
Income tax expense									7,341	7,281	9,054
Net income									27,763	20,296	17,165
Total assets at end of year	1,120,636				733,384				1,120,636	733,384	618,281
Intersegment Eliminations
Segment Reporting Information [Line Items]
Net interest income									21,480	18,629	17,356
Provision for credit losses									0	0	0
Non-interest income									(47,068)	(40,312)	(36,565)
Non-interest expense									(25,588)	(21,683)	(19,209)
Income tax expense									0	0	0
Net income									0	0	0
Total assets at end of year	$ 0				$ 0				$ 0	$ 0	$ 0