Loans and Allowance for Loan Losses (Allowance for Loan Losses by Portfolio Class) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance			$ 217,308	$ 229,418
Allowance for loan losses: Net provision for loan losses	$ 8,891	$ 14,951	21,144	30,942
Allowance for loan losses: Decrease in FDIC loss share receivable				(2,526)
Reduction as a result of sale of subsidiary			(6,648)
Allowance for loan losses: Ending balance	214,530	221,865	214,530	221,865
Allowance for loan losses: Individually evaluated for impairment	20,830	24,896	20,830	24,896
Allowance for loan losses: Amounts related to purchased credit impaired loans	12,378	15,132	12,378	15,132
Allowance for loan losses: Collectively evaluated for impairment	181,322	181,837	181,322	181,837
Loans: Individually evaluated for impairment	331,303	278,015	331,303	278,015
Loans: Purchased credit impaired loans	140,606	163,155	140,606	163,155
Loans: Collectively evaluated for impairment	18,899,008	18,032,671	18,899,008	18,032,671
Loans receivable	19,370,917	18,473,841	19,370,917	18,473,841	$ 19,004,163
Total Commercial [Member] \| Commercial Real Estate - Income Producing [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance			13,709	13,509
Allowance for loan losses: Decrease in FDIC loss share receivable
Reduction as a result of sale of subsidiary
Allowance for loan losses: Ending balance	14,145	13,540	14,145	13,540
Allowance for loan losses: Individually evaluated for impairment	407	1,402	407	1,402
Allowance for loan losses: Amounts related to purchased credit impaired loans	46	192	46	192
Allowance for loan losses: Collectively evaluated for impairment	13,692	11,946	13,692	11,946
Loans: Individually evaluated for impairment	8,820	14,913	8,820	14,913
Loans: Purchased credit impaired loans	3,800	6,247	3,800	6,247
Loans: Collectively evaluated for impairment	2,329,572	2,380,513	2,329,572	2,380,513
Loans receivable	2,342,192	2,401,673	2,342,192	2,401,673	2,384,599
Total Commercial [Member] \| Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance			7,372	6,271
Allowance for loan losses: Decrease in FDIC loss share receivable
Reduction as a result of sale of subsidiary
Allowance for loan losses: Ending balance	10,311	7,049	10,311	7,049
Allowance for loan losses: Individually evaluated for impairment	1	1	1	1
Allowance for loan losses: Amounts related to purchased credit impaired loans	115	239	115	239
Allowance for loan losses: Collectively evaluated for impairment	10,195	6,809	10,195	6,809
Loans: Individually evaluated for impairment	113	847	113	847
Loans: Purchased credit impaired loans	4,769	4,160	4,769	4,160
Loans: Collectively evaluated for impairment	1,510,351	1,308,515	1,510,351	1,308,515
Loans receivable	1,515,233	1,313,522	1,515,233	1,313,522	1,373,421
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance			24,844	25,361
Allowance for loan losses: Decrease in FDIC loss share receivable				(2,344)
Reduction as a result of sale of subsidiary
Allowance for loan losses: Ending balance	24,196	23,380	24,196	23,380
Allowance for loan losses: Individually evaluated for impairment	99	172	99	172
Allowance for loan losses: Amounts related to purchased credit impaired loans	10,873	12,622	10,873	12,622
Allowance for loan losses: Collectively evaluated for impairment	13,224	10,586	13,224	10,586
Loans: Individually evaluated for impairment	3,733	3,466	3,733	3,466
Loans: Purchased credit impaired loans	111,805	129,198	111,805	129,198
Loans: Collectively evaluated for impairment	2,664,821	2,361,259	2,664,821	2,361,259
Loans receivable	2,780,359	2,493,923	2,780,359	2,493,923	2,690,472
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance			30,503	26,142
Allowance for loan losses: Decrease in FDIC loss share receivable				(135)
Reduction as a result of sale of subsidiary			(6,648)
Allowance for loan losses: Ending balance	25,150	28,435	25,150	28,435
Allowance for loan losses: Individually evaluated for impairment	130	283	130	283
Allowance for loan losses: Amounts related to purchased credit impaired loans	497	942	497	942
Allowance for loan losses: Collectively evaluated for impairment	24,523	27,210	24,523	27,210
Loans: Individually evaluated for impairment	599	1,053	599	1,053
Loans: Purchased credit impaired loans	5,381	8,280	5,381	8,280
Loans: Collectively evaluated for impairment	2,082,398	2,083,954	2,082,398	2,083,954
Loans receivable	2,088,378	2,093,287	2,088,378	2,093,287	2,115,295
Non-Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs			(33,935)	(43,103)
Allowance for loan losses: Recoveries			16,661	7,134
Allowance for loan losses: Net provision for loan losses			21,144	30,942
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			(1,604)	(160)
Allowance for loan losses: Recoveries			65	398
Allowance for loan losses: Net provision for loan losses			1,975	(207)
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			(220)	(172)
Allowance for loan losses: Recoveries			38	755
Allowance for loan losses: Net provision for loan losses			3,121	195
Non-Purchased Credit Impaired Loans [Member] \| Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs			(498)	(776)
Allowance for loan losses: Recoveries			712	281
Allowance for loan losses: Net provision for loan losses			(862)	858
Non-Purchased Credit Impaired Loans [Member] \| Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs			(12,964)	(15,260)
Allowance for loan losses: Recoveries			3,095	3,546
Allowance for loan losses: Net provision for loan losses			11,164	14,142
Total Commercial And Industrial [Member] \| Total Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance			140,880	158,135
Allowance for loan losses: Decrease in FDIC loss share receivable				(47)
Reduction as a result of sale of subsidiary
Allowance for loan losses: Ending balance	140,728	149,461	140,728	149,461
Allowance for loan losses: Individually evaluated for impairment	20,193	23,038	20,193	23,038
Allowance for loan losses: Amounts related to purchased credit impaired loans	847	1,137	847	1,137
Allowance for loan losses: Collectively evaluated for impairment	119,688	125,286	119,688	125,286
Loans: Individually evaluated for impairment	318,038	257,736	318,038	257,736
Loans: Purchased credit impaired loans	14,851	15,270	14,851	15,270
Loans: Collectively evaluated for impairment	10,311,866	9,898,430	10,311,866	9,898,430
Loans receivable	10,644,755	10,171,436	10,644,755	10,171,436	10,440,376
Total Commercial And Industrial [Member] \| Total Commercial [Member] \| Commercial Non-Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance			127,918	147,052
Allowance for loan losses: Decrease in FDIC loss share receivable				(47)
Reduction as a result of sale of subsidiary
Allowance for loan losses: Ending balance	126,568	137,363	126,568	137,363
Allowance for loan losses: Individually evaluated for impairment	19,369	22,758	19,369	22,758
Allowance for loan losses: Amounts related to purchased credit impaired loans	427	395	427	395
Allowance for loan losses: Collectively evaluated for impairment	106,772	114,210	106,772	114,210
Loans: Individually evaluated for impairment	291,071	250,256	291,071	250,256
Loans: Purchased credit impaired loans	8,221	5,422	8,221	5,422
Loans: Collectively evaluated for impairment	8,111,669	7,837,426	8,111,669	7,837,426
Loans receivable	8,410,961	8,093,104	8,410,961	8,093,104	8,297,937
Total Commercial And 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			12,962	11,083
Allowance for loan losses: Decrease in FDIC loss share receivable
Reduction as a result of sale of subsidiary
Allowance for loan losses: Ending balance	14,160	12,098	14,160	12,098
Allowance for loan losses: Individually evaluated for impairment	824	280	824	280
Allowance for loan losses: Amounts related to purchased credit impaired loans	420	742	420	742
Allowance for loan losses: Collectively evaluated for impairment	12,916	11,076	12,916	11,076
Loans: Individually evaluated for impairment	26,967	7,480	26,967	7,480
Loans: Purchased credit impaired loans	6,630	9,848	6,630	9,848
Loans: Collectively evaluated for impairment	2,200,197	2,061,004	2,200,197	2,061,004
Loans receivable	$ 2,233,794	$ 2,078,332	2,233,794	2,078,332	$ 2,142,439
Total Commercial And 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			(18,649)	(26,735)
Allowance for loan losses: Recoveries			12,751	2,154
Allowance for loan losses: Net provision for loan losses			5,746	15,954
Total Commercial And 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			(11,845)	(26,218)
Allowance for loan losses: Recoveries			12,476	1,818
Allowance for loan losses: Net provision for loan losses			(1,981)	14,758
Total Commercial And 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			(6,804)	(517)
Allowance for loan losses: Recoveries			275	336
Allowance for loan losses: Net provision for loan losses			$ 7,727	$ 1,196

Financing Receivable, Increase (Decrease) From Sale Of Subsidiary

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- Definition

Reserve for loans impairments recorded after acquisition as a result of current information and events which result in it being probable that estimated cash flows will be less than previously expected or because actual cash flows are less than cash flows previously expected. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

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- Definition

The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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Change in carrying amount of the indemnification asset relating to loss sharing agreements with the Federal Deposit Insurance Corporation (FDIC). The change includes for example, but is not limited to, acquisitions, additional estimated losses, disposals, cash payments, accretion of discount and write-offs, net of recoveries.

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A valuation allowance for financing receivables that are expected to be uncollectible.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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Amount of direct write-downs of financing receivables charged against the allowance.

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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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