Common Stock (Schedule of Restricted Stock) (Details) - Restricted Stock - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Share based compensation, outstanding at beginning of period, in shares	[1]	109,393
Shares awards, number of shares awarded in period		70,273
Total vested, in shares		(68,470)
Total forfeitures, in shares		(4,961)
Share based compensation, outstanding at end of period, in shares	[1]	106,235	109,393
Shares outstanding, weighted average grant date fair value,beginning of period		$ 39.90
Weighted average fair value per share		49.78	$ 40.95	$ 37.17
Weighted average fair value vested		40.93
Weighted average fair value forfeitures		40.18
Shares outstanding, weighted average grant date fair value, end of period		$ 45.76	$ 39.90
Unrecognized compensation expense at end of period	[2]	$ 2,005
Aggregated intrinsic value for shares outstanding at end of period		$ 5,880
Unrecognized compensation expense, period for recognition		1 year

[1] (b) Excludes the stock based retention grant to the President and Chief Executive Officer ("CEO") of 27,624 shares. See "Restricted Stock with a Market Condition (Performance Shares)" section below for further details.

[2] The unrecognized compensation expense is expected to be recognized over the weighted average remaining contractual term of the outstanding restricted stock of approximately one year.