Employee Benefit Plans, Restricted Stock Plan (Details) - Restricted Stock [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)	150,000
Number of shares available for grant (in shares)	145,740
Shares [Roll Forward]
Outstanding, beginning of period (in shares)	8,471
Granted (in shares)	150
Vested (in shares)	(162)
Outstanding, end of period (in shares)	8,459
Weighted Average Market Price [Roll Forward]
Outstanding, beginning of period (in dollars per share)	$ 49.10
Granted (in dollars per share)	51.13
Vested (in dollars per share)	(51.24)
Outstanding, end of period (in dollars per share)	$ 49.10
Additional General Disclosures [Abstract]
Share-based compensation expense	$ 50	$ 47
Compensation cost related to nonvested awards that has not yet been recognized	$ 415
Period over which compensation cost is expected to be recognized	3 years