Nature of Operations and Significant Accounting Policies - Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental disclosure of certain cash and cash equivalents
Interest	$ 11,826	$ 9,256	$ 8,295
Income taxes, net	8,950	9,919	11,061
Loans transferred to held for sale	60	1,628	7,087
Loans transferred to OREO			$ 2,660
Trade date accounting for investment securities	1,553	795
Available for sale securities transferred to held to maturity		288,598
Cash and Cash Equivalents
Supplemental disclosure of certain cash and cash equivalents
Regulatory reserve requirement, balance	$ 24,300	$ 18,200