Loans - (Impaired Loans - Average Recorded Investment and Interest Income Recognized) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Loans [Line Items]
Impaired Financing Receivable, Average Recorded Investment	$ 40,766	$ 56,447
Impaired Financing Receivable, Interest Income, Cash Basis Method	119	153
Commercial and Industrial [Member]
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	8,095	4,919
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	48	68
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	3,445	4,479
Owner-Occupied [Member]
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,885	1,912
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	18	29
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	678	889
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	5	4
Agriculture [Member]
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,588	1,758
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	156	180
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	1	1
Energy Loans [Member]
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	6,098
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	6,589	32,068
Commercial Loan [Member]
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	20,666	8,589
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	66	97
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	10,868	37,616
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	6	5
Commercial Construction [Member]
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		189
Multifamily [Member]
Loans [Line Items]
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	32	36
Non Owner-Occupied [Member]
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	329	719
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	7
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	223	833
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	3	15
Total Commercial Real Estate [Member]
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	329	908
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	7
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	255	869
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	3	15
Senior lien
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,047	1,376
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	3	4
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	5,791	4,799
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	21	19
Junior lien
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		289
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,625	1,937
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	13	13
Residential Real Estate Segment [Member]
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,047	1,665
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	3	4
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	7,416	6,736
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	34	32
Consumer [Member]
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	181	64
Impaired Loans With No Related Allowance Recorded [Member] [Member]
Loans [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	22,046	11,162
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	76	101
Impaired Loans With Related Allowance Recorded [Member]
Loans [Line Items]
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	18,720	45,285
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	$ 43	$ 52