Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Dividend declared (in dollars per share)	$ 0.3250	$ 1.2800
Deferred compensation plan held Rabbi Trust (shares)	93,422	90,961
Preferred Stock, Shares Authorized	2,000,000	2,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Proceeds from Issuance of Common Stock		$ (10)
Shares issued under the performance incentive plan withheld for employee taxes (shares)	10,436	10,269