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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 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	$ 8,088	$ 8,891	26,131	21,144
Reduction as a result of sale of subsidiary				(6,648)
Allowance for loan losses: Ending balance	195,625	214,530	195,625	214,530
Allowance for loan losses: Individually evaluated for impairment	9,121	20,830	9,121	20,830
Allowance for loan losses: Amounts related to purchased credit impaired loans	9,574	12,378	9,574	12,378
Allowance for loan losses: Collectively evaluated for impairment	176,930	181,322	176,930	181,322
Loans: Individually evaluated for impairment	249,881	331,303	249,881	331,303
Loans: Purchased credit impaired loans	119,994	140,606	119,994	140,606
Loans: Collectively evaluated for impairment	19,805,937	18,899,008	19,805,937	18,899,008
Loans receivable	20,175,812	19,370,917	20,175,812	19,370,917	$ 20,026,411
Non-Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Charge-offs			(30,340)	(33,935)
Allowance for loan losses: Recoveries			5,320	16,661
Allowance for loan losses: Net provision for loan losses			26,131	21,144
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	25,411	14,145	25,411	14,145
Allowance for loan losses: Individually evaluated for impairment	93	407	93	407
Allowance for loan losses: Amounts related to purchased credit impaired loans	105	46	105	46
Allowance for loan losses: Collectively evaluated for impairment	25,213	13,692	25,213	13,692
Loans: Individually evaluated for impairment	1,880	8,820	1,880	8,820
Loans: Purchased credit impaired loans	4,702	3,800	4,702	3,800
Loans: Collectively evaluated for impairment	2,888,886	2,329,572	2,888,886	2,329,572
Loans receivable	2,895,468	2,342,192	2,895,468	2,342,192	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	11,665	10,311	11,665	10,311
Allowance for loan losses: Individually evaluated for impairment	1	1	1	1
Allowance for loan losses: Amounts related to purchased credit impaired loans	151	115	151	115
Allowance for loan losses: Collectively evaluated for impairment	11,513	10,195	11,513	10,195
Loans: Individually evaluated for impairment	19	113	19	113
Loans: Purchased credit impaired loans	1,482	4,769	1,482	4,769
Loans: Collectively evaluated for impairment	1,142,561	1,510,351	1,142,561	1,510,351
Loans receivable	1,144,062	1,515,233	1,144,062	1,515,233	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)	(1,604)
Allowance for loan losses: Recoveries			2	65
Allowance for loan losses: Net provision for loan losses			7,781	1,975
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				(220)
Allowance for loan losses: Recoveries			97	38
Allowance for loan losses: Net provision for loan losses			(4,079)	3,121
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	110,762	140,728	110,762	140,728
Allowance for loan losses: Individually evaluated for impairment	8,628	20,193	8,628	20,193
Allowance for loan losses: Amounts related to purchased credit impaired loans	310	847	310	847
Allowance for loan losses: Collectively evaluated for impairment	101,824	119,688	101,824	119,688
Loans: Individually evaluated for impairment	242,372	318,038	242,372	318,038
Loans: Purchased credit impaired loans	11,894	14,851	11,894	14,851
Loans: Collectively evaluated for impairment	10,824,822	10,311,866	10,824,822	10,311,866
Loans receivable	11,079,088	10,644,755	11,079,088	10,644,755	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	96,527	126,568	96,527	126,568
Allowance for loan losses: Individually evaluated for impairment	8,486	19,369	8,486	19,369
Allowance for loan losses: Amounts related to purchased credit impaired loans	138	427	138	427
Allowance for loan losses: Collectively evaluated for impairment	87,903	106,772	87,903	106,772
Loans: Individually evaluated for impairment	224,603	291,071	224,603	291,071
Loans: Purchased credit impaired loans	6,313	8,221	6,313	8,221
Loans: Collectively evaluated for impairment	8,328,202	8,111,669	8,328,202	8,111,669
Loans receivable	8,559,118	8,410,961	8,559,118	8,410,961	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	14,235	14,160	14,235	14,160
Allowance for loan losses: Individually evaluated for impairment	142	824	142	824
Allowance for loan losses: Amounts related to purchased credit impaired loans	172	420	172	420
Allowance for loan losses: Collectively evaluated for impairment	13,921	12,916	13,921	12,916
Loans: Individually evaluated for impairment	17,769	26,967	17,769	26,967
Loans: Purchased credit impaired loans	5,581	6,630	5,581	6,630
Loans: Collectively evaluated for impairment	2,496,620	2,200,197	2,496,620	2,200,197
Loans receivable	2,519,970	2,233,794	2,519,970	2,233,794	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			(21,724)	(18,649)
Allowance for loan losses: Recoveries			2,951	12,751
Allowance for loan losses: Net provision for loan losses			18,026	5,746
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			(21,653)	(11,845)
Allowance for loan losses: Recoveries			2,730	12,476
Allowance for loan losses: Net provision for loan losses			17,698	(1,981)
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			(71)	(6,804)
Allowance for loan losses: Recoveries			221	275
Allowance for loan losses: Net provision for loan losses			328	7,727
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	23,058	24,196	23,058	24,196
Allowance for loan losses: Individually evaluated for impairment	146	99	146	99
Allowance for loan losses: Amounts related to purchased credit impaired loans	8,695	10,873	8,695	10,873
Allowance for loan losses: Collectively evaluated for impairment	14,217	13,224	14,217	13,224
Loans: Individually evaluated for impairment	4,089	3,733	4,089	3,733
Loans: Purchased credit impaired loans	98,472	111,805	98,472	111,805
Loans: Collectively evaluated for impairment	2,865,710	2,664,821	2,865,710	2,664,821
Loans receivable	2,968,271	2,780,359	2,968,271	2,780,359	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			(439)	(498)
Allowance for loan losses: Recoveries			266	712
Allowance for loan losses: Net provision for loan losses			(551)	(862)
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	24,729	25,150	24,729	25,150
Allowance for loan losses: Individually evaluated for impairment	253	130	253	130
Allowance for loan losses: Amounts related to purchased credit impaired loans	313	497	313	497
Allowance for loan losses: Collectively evaluated for impairment	24,163	24,523	24,163	24,523
Loans: Individually evaluated for impairment	1,521	599	1,521	599
Loans: Purchased credit impaired loans	3,444	5,381	3,444	5,381
Loans: Collectively evaluated for impairment	2,083,958	2,082,398	2,083,958	2,082,398
Loans receivable	$ 2,088,923	$ 2,088,378	2,088,923	2,088,378	$ 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			(8,167)	(12,964)
Allowance for loan losses: Recoveries			2,004	3,095
Allowance for loan losses: Net provision for loan losses			$ 4,954	$ 11,164

Financing Receivable, Increase (Decrease) From Sale Of Subsidiary

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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.

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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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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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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 individually evaluated for impairment.

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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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