Loans - Impaired Loans Summary (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Impaired loans summary
Nonaccrual loans	$ 59,338,000		$ 66,673,000
Accruing loans past due 90 days or more	5,500,000		1,169,000
Restructured loans - nonaccrual	10,276,000		10,133,000
Restructured loans - accruing	11,068,000		16,518,000
Total nonperforming loans	86,182,000		94,493,000
Impaired loans, other information
Total nonaccrual loans	69,600,000		76,800,000
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	1,700,000	$ 890,000
Reserved based energy loans
Impaired loans, other information
Impaired Financing Receivable, with Related Allowance, Recorded Investment	14,100,000		14,000,000
Energy related service industry loans
Impaired loans, other information
Impaired Financing Receivable, with Related Allowance, Recorded Investment	35,600,000		42,200
Originated
Impaired loans summary
Nonaccrual loans	38,058,000		32,805,000
Accruing loans past due 90 days or more	3,842,000		1,169,000
Restructured loans - nonaccrual	6,959,000		6,959,000
Restructured loans - accruing	145,000		5,267,000
Total nonperforming loans	49,004,000		46,200,000
Impaired loans, other information
Impaired Financing Receivable, with Related Allowance, Recorded Investment	23,005,000		3,111,000
Acquired
Impaired loans summary
Nonaccrual loans	21,280,000		33,868,000
Accruing loans past due 90 days or more	1,658,000
Restructured loans - nonaccrual	3,317,000		3,174,000
Restructured loans - accruing	10,923,000		11,251,000
Total nonperforming loans	37,178,000		48,293,000
Impaired loans, other information
Impaired Financing Receivable, with Related Allowance, Recorded Investment	$ 5,927,000		$ 1,755,000