Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Tax provision on defined benefit pension plans	$ (491)	$ 25	$ (463)	$ 51
Tax provision on loss on derivative instrument classified as a cash flow hedge	$ 402	$ 229	$ 532	$ 144