CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Minimum pension liability adjustment, tax expense	$ (6,135)	$ (2,071)	$ (10,853)
Unrealized benefit (loss) on interest rate swaps and cash flow hedges , tax expense (benefit)	$ 52	$ (135)	$ 380
Cash dividend per share	$ 0.56	$ 0.56	$ 0.56	[1]
Accumulated Other Comprehensive Income (Loss) [Member]
Minimum pension liability adjustment, tax expense	$ (6,135)	$ (2,071)	$ (10,853)
Unrealized benefit (loss) on interest rate swaps and cash flow hedges , tax expense (benefit)	$ 52	$ (135)	$ 380
Retained Earnings [Member]
Cash dividend per share	$ 0.56	$ 0.56	$ 0.56

[1] Revised in 2015 for the impact of the changes in accounting principle related to inventory accounting.