Loans and Allowance for Loan Losses (Allowance for Loan Losses by Portfolio Class) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	$ 229,418	$ 181,179
Allowance for loan losses: Net provision for loan losses	15,991	60,036
Allowance for loan losses: Decrease in FDIC loss share receivable	(1,830)	(2,189)
Allowance for loan losses: Ending balance	213,550	217,794
Allowance for loan losses: Individually evaluated for impairment	16,501	28,167
Allowance for loan losses: Amounts related to purchased credit impaired loans	15,999	20,502
Allowance for loan losses: Collectively evaluated for impairment	181,050	169,125
Loans: Individually evaluated for impairment	256,458	230,741
Loans: Purchased credit impaired loans	179,367	221,893	$ 190,915	$ 225,838
Loans: Collectively evaluated for impairment	17,769,043	15,525,490
Loans: Total loans	18,204,868	15,978,124	16,752,151
Total Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans: Total loans	13,879,509		12,545,507
Total Commercial [Member] | Commercial Real Estate - Income Producing [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	13,509	6,041
Allowance for loan losses: Ending balance	13,611	7,593
Allowance for loan losses: Individually evaluated for impairment	1,114	1,272
Allowance for loan losses: Amounts related to purchased credit impaired loans	213	605
Allowance for loan losses: Collectively evaluated for impairment	12,284	5,716
Loans: Individually evaluated for impairment	13,599	8,681
Loans: Purchased credit impaired loans	7,669	11,185
Loans: Collectively evaluated for impairment	2,483,836	1,732,879
Loans: Total loans	2,505,104	1,752,745	2,013,890
Total Commercial [Member] | Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	6,271	5,642
Allowance for loan losses: Ending balance	6,720	4,376
Allowance for loan losses: Individually evaluated for impairment	1	185
Allowance for loan losses: Amounts related to purchased credit impaired loans	283	523
Allowance for loan losses: Collectively evaluated for impairment	6,436	3,668
Loans: Individually evaluated for impairment	1,592	14,072
Loans: Purchased credit impaired loans	4,326	8,930
Loans: Collectively evaluated for impairment	1,246,749	1,072,412
Loans: Total loans	1,252,667	1,095,414	1,010,879
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	25,361	25,353
Allowance for loan losses: Ending balance	23,806	24,692
Allowance for loan losses: Individually evaluated for impairment	94	125
Allowance for loan losses: Amounts related to purchased credit impaired loans	13,286	16,641
Allowance for loan losses: Collectively evaluated for impairment	10,426	7,926
Loans: Individually evaluated for impairment	3,236	883
Loans: Purchased credit impaired loans	138,260	161,078
Loans: Collectively evaluated for impairment	2,124,767	1,839,006
Loans: Total loans	2,266,263	2,000,967	2,146,713
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	26,142	24,857
Allowance for loan losses: Ending balance	26,622	21,878
Allowance for loan losses: Individually evaluated for impairment	199	16
Allowance for loan losses: Amounts related to purchased credit impaired loans	1,019	1,388
Allowance for loan losses: Collectively evaluated for impairment	25,404	20,474
Loans: Individually evaluated for impairment	2,149	58
Loans: Purchased credit impaired loans	9,951	12,177
Loans: Collectively evaluated for impairment	2,046,996	2,048,010
Loans: Total loans	2,059,096	2,060,245	2,059,931
Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(252)	(47)
Allowance for loan losses: Recoveries	134	114
Allowance for loan losses: Net provision for loan losses	(406)	(496)
Allowance for loan losses: Decrease in FDIC loss share receivable	(1,830)	(2,189)
Purchased Credit Impaired Loans [Member] | Total Commercial [Member] | Commercial Real Estate - Income Producing [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs		(1)
Allowance for loan losses: Recoveries		1
Allowance for loan losses: Net provision for loan losses	(40)	(109)
Allowance for loan losses: Decrease in FDIC loss share receivable
Purchased Credit Impaired Loans [Member] | Total Commercial [Member] | Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(54)	(18)
Allowance for loan losses: Recoveries	23	35
Allowance for loan losses: Net provision for loan losses	(92)	(151)
Allowance for loan losses: Decrease in FDIC loss share receivable
Purchased Credit Impaired Loans [Member] | Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(59)
Allowance for loan losses: Recoveries	5	1
Allowance for loan losses: Net provision for loan losses	(7)	1,130
Allowance for loan losses: Decrease in FDIC loss share receivable	(1,696)	(2,153)
Purchased Credit Impaired Loans [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(139)
Allowance for loan losses: Recoveries	29	39
Allowance for loan losses: Net provision for loan losses	(39)	(1,179)
Allowance for loan losses: Decrease in FDIC loss share receivable	(103)	(19)
Non-Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(33,692)	(24,693)
Allowance for loan losses: Recoveries	3,781	3,394
Allowance for loan losses: Net provision for loan losses	16,397	60,532
Non-Purchased Credit Impaired Loans [Member] | Total Commercial [Member] | Commercial Real Estate - Income Producing [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(7)	(115)
Allowance for loan losses: Recoveries	375	144
Allowance for loan losses: Net provision for loan losses	(226)	1,632
Non-Purchased Credit Impaired Loans [Member] | Total Commercial [Member] | Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(37)	(110)
Allowance for loan losses: Recoveries	448	605
Allowance for loan losses: Net provision for loan losses	161	(1,627)
Non-Purchased Credit Impaired Loans [Member] | Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(289)	(175)
Allowance for loan losses: Recoveries	108	301
Allowance for loan losses: Net provision for loan losses	383	235
Non-Purchased Credit Impaired Loans [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(8,539)	(5,843)
Allowance for loan losses: Recoveries	1,714	1,494
Allowance for loan losses: Net provision for loan losses	7,557	2,529
Total Commercial & Industrial [Member] | Total Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	158,135	119,286
Allowance for loan losses: Ending balance	142,791	159,255
Allowance for loan losses: Individually evaluated for impairment	15,093	26,569
Allowance for loan losses: Amounts related to purchased credit impaired loans	1,198	1,345
Allowance for loan losses: Collectively evaluated for impairment	126,500	131,341
Loans: Individually evaluated for impairment	235,882	207,047
Loans: Purchased credit impaired loans	19,161	28,523
Loans: Collectively evaluated for impairment	9,866,695	8,833,183
Loans: Total loans	10,121,738	9,068,753	9,520,738
Total Commercial & Industrial [Member] | Total Commercial [Member] | Commercial Non-Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	147,052	109,428
Allowance for loan losses: Ending balance	131,269	144,659
Allowance for loan losses: Individually evaluated for impairment	15,017	26,502
Allowance for loan losses: Amounts related to purchased credit impaired loans	411	439
Allowance for loan losses: Collectively evaluated for impairment	115,841	117,718
Loans: Individually evaluated for impairment	231,988	201,029
Loans: Purchased credit impaired loans	6,693	12,659
Loans: Collectively evaluated for impairment	7,835,606	6,931,718
Loans: Total loans	8,074,287	7,145,406	7,613,917
Total Commercial & Industrial [Member] | Total Commercial [Member] | Commercial Real Estate - Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	11,083	9,858
Allowance for loan losses: Ending balance	11,522	14,596
Allowance for loan losses: Individually evaluated for impairment	76	67
Allowance for loan losses: Amounts related to purchased credit impaired loans	787	906
Allowance for loan losses: Collectively evaluated for impairment	10,659	13,623
Loans: Individually evaluated for impairment	3,894	6,018
Loans: Purchased credit impaired loans	12,468	15,864
Loans: Collectively evaluated for impairment	2,031,089	1,901,465
Loans: Total loans	2,047,451	1,923,347	$ 1,906,821
Total Commercial & Industrial [Member] | Purchased Credit Impaired Loans [Member] | Total Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs		(28)
Allowance for loan losses: Recoveries	77	38
Allowance for loan losses: Net provision for loan losses	(228)	(187)
Allowance for loan losses: Decrease in FDIC loss share receivable	(31)	(17)
Total Commercial & Industrial [Member] | Purchased Credit Impaired Loans [Member] | Total Commercial [Member] | Commercial Non-Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs
Allowance for loan losses: Recoveries	2	3
Allowance for loan losses: Net provision for loan losses	(46)	7
Allowance for loan losses: Decrease in FDIC loss share receivable	(31)	(17)
Total Commercial & Industrial [Member] | Purchased Credit Impaired Loans [Member] | Total Commercial [Member] | Commercial Real Estate - Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs		(28)
Allowance for loan losses: Recoveries	75	35
Allowance for loan losses: Net provision for loan losses	(182)	(194)
Allowance for loan losses: Decrease in FDIC loss share receivable
Total Commercial & Industrial [Member] | Non-Purchased Credit Impaired Loans [Member] | Total Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(24,820)	(18,450)
Allowance for loan losses: Recoveries	1,136	850
Allowance for loan losses: Net provision for loan losses	8,522	57,763
Total Commercial & Industrial [Member] | Non-Purchased Credit Impaired Loans [Member] | Total Commercial [Member] | Commercial Non-Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(24,791)	(17,667)
Allowance for loan losses: Recoveries	936	809
Allowance for loan losses: Net provision for loan losses	8,147	52,096
Total Commercial & Industrial [Member] | Non-Purchased Credit Impaired Loans [Member] | Total Commercial [Member] | Commercial Real Estate - Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(29)	(783)
Allowance for loan losses: Recoveries	200	41
Allowance for loan losses: Net provision for loan losses	$ 375	$ 5,667