Loans - Average recorded investment and interest income recognized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 71,766	$ 99,679	$ 79,067	$ 71,269
Interest income recognized	275	382	610	757
Originated
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	46,666	71,777	45,754	58,760
Interest income recognized	145	192	185	566
Originated | Commercial & Industrial
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	41,829	62,932	39,892	51,141
Interest income recognized	47	38	59	57
Originated | Owner occupied commercial real estate
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		1,498		1,030
Interest income recognized		73		73
Originated | Commercial real estate
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	723	6,589	2,744	5,718
Interest income recognized		80		241
Originated | Construction, land & land development
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	3,016		1,005	205
Interest income recognized				180
Originated | Residential mortgage
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,023	575	1,977	531
Interest income recognized	97		123	10
Originated | Consumer and other
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	75	183	136	135
Interest income recognized	1	1	3	5
Acquired
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	25,100	27,902	33,313	12,509
Interest income recognized	130	190	425	191
Acquired | Commercial & Industrial
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	16,693	20,362	21,989	7,372
Interest income recognized	77	63	348	63
Acquired | Owner occupied commercial real estate
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	6,918	3,029	7,977	1,431
Acquired | Commercial real estate
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	42	2,304	1,093	1,932
Interest income recognized		48		48
Acquired | Construction, land & land development
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,021	239	1,186	79
Interest income recognized	30		45
Acquired | Residential mortgage
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	212	1,959	900	1,691
Interest income recognized	23	79	32	80
Acquired | Consumer and other
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 214	$ 9	$ 168	$ 4