Employee Benefit Plans, Restricted Stock Plan (Details) - Restricted Stock [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Deferred Compensation Arrangements [Abstract]
Number of shares authorized (in shares)	150,000
Number of shares available for grant (in shares)	135,582
Unvested Shares [Roll Forward]
Outstanding, beginning of period (in shares)	9,764
Granted (in shares)	0
Forfeited (in shares)	0
Vested (in shares)	(50)
Outstanding, end of period (in shares)	9,714
Weighted Average Market Price [Roll Forward]
Outstanding, beginning of period (in dollars per share)	$ 58.21
Granted (in dollars per share)	0
Forfeited (in dollars per share)	0
Vested (in dollars per share)	(51.13)
Outstanding, end of period (in dollars per share)	$ 58.25
Additional General Disclosures [Abstract]
Share-based compensation expense	$ 67	$ 56
Compensation cost related to nonvested awards that has not yet been recognized	$ 566
Period over which compensation cost is expected to be recognized	3 years