Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Loans, principally due to allowance for loan losses	$ 28,285	$ 28,999
Deferred Costs, Leasing, Gross	455	596
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Contingencies	101	108
Deferred Discounts, Finance Charges and Interest Included in Receivables	3,152	4,552
Deferred Tax Assets, Unrealized Losses on Trading Securities	6,602	0
Employee benefits	9,277	9,009
Other real estate owned write-downs and carrying costs	1,270	598
Deferred revenue on contract	912	1,087
Other	1,008	126
Deferred tax assets	51,062	45,075
Deferred tax liabilities:
Fixed assets, principally differences in bases and depreciation	(4,750)	(5,140)
Deferred Tax Liabilities, Unrealized Gains on Available For Sale Securities	0	(445)
Investment in joint venture partnership, principally due to differences in depreciation of partnership assets	(1,192)	(1,301)
Prepaid amounts	(1,523)	(1,139)
Government agency stock dividends	(2,287)	(2,442)
Goodwill and core deposit intangibles	(42,362)	(39,886)
Mortgage servicing rights	(5,467)	(4,422)
Other	(320)	(65)
Deferred tax liabilities	(57,901)	(54,840)
Deferred Tax Liabilities, Net	(6,839)	(9,765)
Income Taxes Payable, Current	$ 5,761	$ 6,275