Consolidated Statements of Shareholder's Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Pension liability, income tax expense (benefit)	$ 378	$ (279)	$ 2,800
Cash flow hedging gain (loss), income tax expense (benefit)	$ (2,975)	$ 202	$ (1,216)