Loans and Allowance for Loan Losses (Allowance for Loan Losses by Portfolio Class) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 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	$ 6,872	$ 13,040	28,016	43,982
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	214,550	223,122	214,550	223,122
Allowance for loan losses: Individually evaluated for impairment	23,906	23,490	23,906	23,490
Allowance for loan losses: Amounts related to purchased credit impaired loans	11,408	15,312	11,408	15,312
Allowance for loan losses: Collectively evaluated for impairment	179,236	184,320	179,236	184,320
Loans: Individually evaluated for impairment	307,081	302,398	307,081	302,398
Loans: Purchased credit impaired loans	135,035	176,111	135,035	176,111
Loans: Collectively evaluated for impairment	19,101,601	18,307,776	19,101,601	18,307,776
Loans receivable	19,543,717	18,786,285	19,543,717	18,786,285	$ 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	18,585	14,490	18,585	14,490
Allowance for loan losses: Individually evaluated for impairment	285	1,321	285	1,321
Allowance for loan losses: Amounts related to purchased credit impaired loans	45	199	45	199
Allowance for loan losses: Collectively evaluated for impairment	18,255	12,970	18,255	12,970
Loans: Individually evaluated for impairment	4,615	14,295	4,615	14,295
Loans: Purchased credit impaired loans	3,790	5,353	3,790	5,353
Loans: Collectively evaluated for impairment	2,303,294	2,492,160	2,303,294	2,492,160
Loans receivable	2,311,699	2,511,808	2,311,699	2,511,808	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	13,423	6,581	13,423	6,581
Allowance for loan losses: Individually evaluated for impairment	1	1	1	1
Allowance for loan losses: Amounts related to purchased credit impaired loans	91	254	91	254
Allowance for loan losses: Collectively evaluated for impairment	13,331	6,326	13,331	6,326
Loans: Individually evaluated for impairment	112	480	112	480
Loans: Purchased credit impaired loans	4,232	6,670	4,232	6,670
Loans: Collectively evaluated for impairment	1,519,075	1,365,898	1,519,075	1,365,898
Loans receivable	1,523,419	1,373,048	1,523,419	1,373,048	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	24,310	25,034	24,310	25,034
Allowance for loan losses: Individually evaluated for impairment	163	406	163	406
Allowance for loan losses: Amounts related to purchased credit impaired loans	10,109	12,795	10,109	12,795
Allowance for loan losses: Collectively evaluated for impairment	14,038	11,833	14,038	11,833
Loans: Individually evaluated for impairment	3,061	8,942	3,061	8,942
Loans: Purchased credit impaired loans	107,535	123,244	107,535	123,244
Loans: Collectively evaluated for impairment	2,736,320	2,464,506	2,736,320	2,464,506
Loans receivable	2,846,916	2,596,692	2,846,916	2,596,692	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	24,437	29,363	24,437	29,363
Allowance for loan losses: Individually evaluated for impairment	131	405	131	405
Allowance for loan losses: Amounts related to purchased credit impaired loans	433	863	433	863
Allowance for loan losses: Collectively evaluated for impairment	23,873	28,095	23,873	28,095
Loans: Individually evaluated for impairment	890	1,306	890	1,306
Loans: Purchased credit impaired loans	4,458	7,637	4,458	7,637
Loans: Collectively evaluated for impairment	2,117,180	2,090,351	2,117,180	2,090,351
Loans receivable	2,122,528	2,099,294	2,122,528	2,099,294	2,115,295
Non-Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs			(43,813)	(61,933)
Allowance for loan losses: Recoveries			19,687	14,181
Allowance for loan losses: Net provision for loan losses			28,016	43,982
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			(1,633)	(160)
Allowance for loan losses: Recoveries			221	655
Allowance for loan losses: Net provision for loan losses			6,288	486
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			(265)	(670)
Allowance for loan losses: Recoveries			68	1,050
Allowance for loan losses: Net provision for loan losses			6,248	(70)
Non-Purchased Credit Impaired Loans [Member] \| Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs			(585)	(2,485)
Allowance for loan losses: Recoveries			1,854	339
Allowance for loan losses: Net provision for loan losses			(1,803)	4,163
Non-Purchased Credit Impaired Loans [Member] \| Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs			(18,599)	(22,844)
Allowance for loan losses: Recoveries			4,028	5,248
Allowance for loan losses: Net provision for loan losses			15,153	20,952
Total Commercial And Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans receivable	10,739,155		10,739,155
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	133,795	147,654	133,795	147,654
Allowance for loan losses: Individually evaluated for impairment	23,326	21,357	23,326	21,357
Allowance for loan losses: Amounts related to purchased credit impaired loans	730	1,201	730	1,201
Allowance for loan losses: Collectively evaluated for impairment	109,739	125,096	109,739	125,096
Loans: Individually evaluated for impairment	298,403	277,375	298,403	277,375
Loans: Purchased credit impaired loans	15,020	33,207	15,020	33,207
Loans: Collectively evaluated for impairment	10,425,732	9,894,861	10,425,732	9,894,861
Loans receivable	10,739,155	10,205,443	10,739,155	10,205,443	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	120,678	134,095	120,678	134,095
Allowance for loan losses: Individually evaluated for impairment	23,101	20,880	23,101	20,880
Allowance for loan losses: Amounts related to purchased credit impaired loans	327	417	327	417
Allowance for loan losses: Collectively evaluated for impairment	97,250	112,798	97,250	112,798
Loans: Individually evaluated for impairment	275,966	271,024	275,966	271,024
Loans: Purchased credit impaired loans	7,907	20,186	7,907	20,186
Loans: Collectively evaluated for impairment	8,155,011	7,838,219	8,155,011	7,838,219
Loans receivable	8,438,884	8,129,429	8,438,884	8,129,429	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	13,117	13,559	13,117	13,559
Allowance for loan losses: Individually evaluated for impairment	225	477	225	477
Allowance for loan losses: Amounts related to purchased credit impaired loans	403	784	403	784
Allowance for loan losses: Collectively evaluated for impairment	12,489	12,298	12,489	12,298
Loans: Individually evaluated for impairment	22,437	6,351	22,437	6,351
Loans: Purchased credit impaired loans	7,113	13,021	7,113	13,021
Loans: Collectively evaluated for impairment	2,270,721	2,056,642	2,270,721	2,056,642
Loans receivable	$ 2,300,271	$ 2,076,014	2,300,271	2,076,014	$ 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			(22,731)	(35,774)
Allowance for loan losses: Recoveries			13,516	6,889
Allowance for loan losses: Net provision for loan losses			2,130	18,451
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			(15,401)	(35,247)
Allowance for loan losses: Recoveries			13,234	6,442
Allowance for loan losses: Net provision for loan losses			(5,073)	15,895
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			(7,330)	(527)
Allowance for loan losses: Recoveries			282	447
Allowance for loan losses: Net provision for loan losses			$ 7,203	$ 2,556

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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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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- Definition

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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