Loans and Allowance for Loan Losses (Allowance for Loan Losses by Portfolio Class) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	$ 194,514	$ 217,308
Allowance for loan losses: Net provision for loan losses	18,043	12,253
Reduction as a result of sale of subsidiary		(6,648)
Allowance for loan losses: Ending balance	194,688	210,713
Allowance for loan losses: Individually evaluated for impairment	2,690	24,601
Allowance for loan losses: Amounts related to purchased credit impaired loans	10,089	14,047
Allowance for loan losses: Collectively evaluated for impairment	181,909	172,065
Loans: Individually evaluated for impairment	258,072	377,370
Loans: Purchased credit impaired loans	124,895	149,383
Loans: Collectively evaluated for impairment	19,729,871	18,565,751
Loans receivable	20,112,838	19,092,504	$ 20,026,411
Non-Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(20,991)	(18,436)
Allowance for loan losses: Recoveries	3,122	6,236
Allowance for loan losses: Net provision for loan losses	18,043	12,253
Total Commercial [Member] \| Commercial Real Estate - Income Producing [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	17,638	13,709
Allowance for loan losses: Ending balance	20,803	12,985
Allowance for loan losses: Individually evaluated for impairment	143	1,261
Allowance for loan losses: Amounts related to purchased credit impaired loans	35	576
Allowance for loan losses: Collectively evaluated for impairment	20,625	11,148
Loans: Individually evaluated for impairment	2,668	14,071
Loans: Purchased credit impaired loans	4,267	4,361
Loans: Collectively evaluated for impairment	2,556,459	2,376,430
Loans receivable	2,563,394	2,394,862	2,341,779
Total Commercial [Member] \| Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	15,647	7,372
Allowance for loan losses: Ending balance	14,027	9,924
Allowance for loan losses: Individually evaluated for impairment	1	1
Allowance for loan losses: Amounts related to purchased credit impaired loans	78	173
Allowance for loan losses: Collectively evaluated for impairment	13,948	9,750
Loans: Individually evaluated for impairment	19	113
Loans: Purchased credit impaired loans	2,897	5,843
Loans: Collectively evaluated for impairment	1,337,151	1,407,922
Loans receivable	1,340,067	1,413,878	1,548,335
Total Commercial [Member] \| Non-Purchased Credit Impaired Loans [Member] \| Commercial Real Estate - Income Producing [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(10)
Allowance for loan losses: Recoveries	2	63
Allowance for loan losses: Net provision for loan losses	3,173	(787)
Total Commercial [Member] \| Non-Purchased Credit Impaired Loans [Member] \| Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs		(10)
Allowance for loan losses: Recoveries	11	29
Allowance for loan losses: Net provision for loan losses	(1,631)	2,533
Total Commercial [Member] \| Total Commercial And Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	111,509	140,880
Allowance for loan losses: Ending balance	111,327	140,226
Allowance for loan losses: Individually evaluated for impairment	1,980	22,831
Allowance for loan losses: Amounts related to purchased credit impaired loans	473	966
Allowance for loan losses: Collectively evaluated for impairment	108,874	116,429
Loans: Individually evaluated for impairment	248,480	354,231
Loans: Purchased credit impaired loans	11,917	16,894
Loans: Collectively evaluated for impairment	10,911,357	10,150,640
Loans receivable	11,171,754	10,521,765	11,078,349
Total Commercial [Member] \| Total Commercial And Industrial [Member] \| Commercial Non-Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	97,752	127,918
Allowance for loan losses: Ending balance	97,520	126,606
Allowance for loan losses: Individually evaluated for impairment	1,775	20,356
Allowance for loan losses: Amounts related to purchased credit impaired loans	288	471
Allowance for loan losses: Collectively evaluated for impairment	95,457	105,779
Loans: Individually evaluated for impairment	231,506	323,913
Loans: Purchased credit impaired loans	6,445	8,510
Loans: Collectively evaluated for impairment	8,418,375	8,003,799
Loans receivable	8,656,326	8,336,222	8,620,601
Total Commercial [Member] \| Total Commercial And Industrial [Member] \| Commercial Real Estate - Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	13,757	12,962
Allowance for loan losses: Ending balance	13,807	13,620
Allowance for loan losses: Individually evaluated for impairment	205	2,475
Allowance for loan losses: Amounts related to purchased credit impaired loans	185	495
Allowance for loan losses: Collectively evaluated for impairment	13,417	10,650
Loans: Individually evaluated for impairment	16,974	30,318
Loans: Purchased credit impaired loans	5,472	8,384
Loans: Collectively evaluated for impairment	2,492,982	2,146,841
Loans receivable	2,515,428	2,185,543	2,457,748
Total Commercial [Member] \| Total Commercial And Industrial [Member] \| Non-Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(16,344)	(10,186)
Allowance for loan losses: Recoveries	1,943	4,234
Allowance for loan losses: Net provision for loan losses	14,219	5,298
Total Commercial [Member] \| Total Commercial And Industrial [Member] \| Non-Purchased Credit Impaired Loans [Member] \| Commercial Non-Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(16,344)	(9,335)
Allowance for loan losses: Recoveries	1,926	4,146
Allowance for loan losses: Net provision for loan losses	14,186	3,877
Total Commercial [Member] \| Total Commercial And Industrial [Member] \| Non-Purchased Credit Impaired Loans [Member] \| Commercial Real Estate - Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs		(851)
Allowance for loan losses: Recoveries	17	88
Allowance for loan losses: Net provision for loan losses	33	1,421
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	23,782	24,844
Allowance for loan losses: Ending balance	23,535	24,918
Allowance for loan losses: Individually evaluated for impairment	219	276
Allowance for loan losses: Amounts related to purchased credit impaired loans	9,162	11,720
Allowance for loan losses: Collectively evaluated for impairment	14,154	12,922
Loans: Individually evaluated for impairment	5,397	8,338
Loans: Purchased credit impaired loans	102,199	116,409
Loans: Collectively evaluated for impairment	2,825,655	2,608,074
Loans receivable	2,933,251	2,732,821	2,910,081
Residential Mortgages [Member] \| Non-Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(406)	(192)
Allowance for loan losses: Recoveries	162	116
Allowance for loan losses: Net provision for loan losses	(3)	150
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Beginning balance	25,938	30,503
Reduction as a result of sale of subsidiary		(6,648)
Allowance for loan losses: Ending balance	24,996	22,660
Allowance for loan losses: Individually evaluated for impairment	347	232
Allowance for loan losses: Amounts related to purchased credit impaired loans	341	612
Allowance for loan losses: Collectively evaluated for impairment	24,308	21,816
Loans: Individually evaluated for impairment	1,508	617
Loans: Purchased credit impaired loans	3,615	5,876
Loans: Collectively evaluated for impairment	2,099,249	2,022,685
Loans receivable	2,104,372	2,029,178	$ 2,147,867
Consumer [Member] \| Non-Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs	(4,231)	(8,048)
Allowance for loan losses: Recoveries	1,004	1,794
Allowance for loan losses: Net provision for loan losses	$ 2,285	$ 5,059

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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
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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.

+ References

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- Definition

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

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-Publisher FASB
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- Definition

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

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- Definition

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

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- Definition

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.

+ References

No definition available.

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- Definition

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

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- Definition

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

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- Definition

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

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- Definition

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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- Definition

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

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