Loans - Age Analysis of Loans (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual status, days past due	90 days
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	$ 22,378	$ 20,461
90 Days or More Past Due	4,828	1,169
Total loans past due and still accruing	27,206	21,630
Nonaccrual	54,211	76,806
Purchased Credit Impaired	20,416	25,188
Current	2,969,928	2,974,596
Loans held for investment	3,071,761	3,098,220	$ 3,047,618
Originated
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	14,144	11,373
90 Days or More Past Due	1,069	1,169
Total loans past due and still accruing	15,213	12,542
Nonaccrual	42,387	39,763
Current	2,427,639	2,249,623
Loans held for investment	2,485,239	2,301,928	2,152,059
Acquired
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	8,234	9,088
90 Days or More Past Due	3,759
Total loans past due and still accruing	11,993	9,088
Nonaccrual	11,824	37,043
Purchased Credit Impaired	20,416	25,188
Current	542,289	724,973
Loans held for investment	586,522	796,292	895,559
Commercial & Industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	1,148,850	1,053,925
Commercial & Industrial | Originated
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	2,800	1,515
90 Days or More Past Due	50	1,106
Total loans past due and still accruing	2,850	2,621
Nonaccrual	37,489	36,331
Current	1,026,376	865,379
Loans held for investment	1,066,715	904,331	823,047
Commercial & Industrial | Acquired
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	218	2,854
Total loans past due and still accruing	218	2,854
Nonaccrual	8,707	23,424
Purchased Credit Impaired	3,339	4,506
Current	69,871	118,810
Loans held for investment	82,135	149,594	181,367
Owner occupied commercial real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	408,398	394,210
Owner occupied commercial real estate | Originated
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	500	1,941
90 Days or More Past Due	357
Total loans past due and still accruing	857	1,941
Current	311,305	262,935
Loans held for investment	312,162	264,876	249,827
Owner occupied commercial real estate | Acquired
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	4,971	223
Total loans past due and still accruing	4,971	223
Nonaccrual	2,634	8,942
Purchased Credit Impaired	4,283	5,339
Current	84,348	114,830
Loans held for investment	96,236	129,334	137,205
Commercial real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	1,068,742	1,143,751
Commercial real estate | Originated
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	5,165	1,612
Total loans past due and still accruing	5,165	1,612
Nonaccrual	202	2,059
Current	800,960	812,358
Loans held for investment	806,327	816,029	761,788
Commercial real estate | Acquired
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	1,082	2,529
90 Days or More Past Due	180
Total loans past due and still accruing	1,262	2,529
Nonaccrual	127	2,002
Purchased Credit Impaired	10,323	10,807
Current	250,703	312,384
Loans held for investment	262,415	327,722	347,854
Construction, land & land development
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	193,856	249,704
Construction, land & land development | Originated
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	1,212	4,375
90 Days or More Past Due	222
Total loans past due and still accruing	1,434	4,375
Nonaccrual	3,137
Current	141,951	175,624
Loans held for investment	146,522	179,999	180,315
Construction, land & land development | Acquired
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	1,144	488
90 Days or More Past Due	3,579
Total loans past due and still accruing	4,723	488
Nonaccrual	107	978
Purchased Credit Impaired	17	1,819
Current	42,487	66,420
Loans held for investment	47,334	69,705	98,008
Residential mortgage
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	235,089	245,191
Residential mortgage | Originated
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	4,383	1,791
90 Days or More Past Due	419	63
Total loans past due and still accruing	4,802	1,854
Nonaccrual	1,507	1,254
Current	131,786	124,337
Loans held for investment	138,095	127,445	128,077
Residential mortgage | Acquired
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	818	2,768
Total loans past due and still accruing	818	2,768
Nonaccrual	37	1,692
Purchased Credit Impaired	2,454	2,717
Current	93,685	110,569
Loans held for investment	96,994	117,746	128,763
Consumer and other
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	16,826	11,439
Consumer and other | Originated
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	84	139
90 Days or More Past Due	21
Total loans past due and still accruing	105	139
Nonaccrual	52	119
Current	15,261	8,990
Loans held for investment	15,418	9,248	9,005
Consumer and other | Acquired
Financing Receivable, Recorded Investment, Aging [Abstract]
30-89 Past Due	1	226
Total loans past due and still accruing	1	226
Nonaccrual	212	5
Current	1,195	1,960
Loans held for investment	$ 1,408	$ 2,191	$ 2,362