Employee Benefit Plans, Restricted Stock Plan (Details) - Restricted Stock [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)	150,000		150,000
Number of shares available for grant (in shares)	141,678		141,678
Unvested Shares [Roll Forward]
Outstanding, beginning of period (in shares)	9,169		8,471
Granted (in shares)	0		4,212
Forfeited (in shares)	0		(43)
Vested (in shares)	0		(3,471)
Outstanding, end of period (in shares)	9,169		9,169
Weighted Average Market Price [Roll Forward]
Outstanding, beginning of period (in dollars per share)	$ 50.66		$ 49.10
Granted (in dollars per share)	0		53.38
Forfeited (in dollars per share)	0		(48.56)
Vested (in dollars per share)	0		(50.19)
Outstanding, end of period (in dollars per share)	$ 50.66		$ 50.66
Additional General Disclosures [Abstract]
Share-based compensation expense	$ 54	$ 50	$ 158	$ 142
Compensation cost related to nonvested awards that has not yet been recognized	$ 464		$ 464
Period over which compensation cost is expected to be recognized			3 years