Retirement Plans - Summary of Categories in Fair Value Hierarchy (Details 9) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair values of pension plan assets
Total	$ 293,567	$ 290,795
Equity Securities | U.S.
Fair values of pension plan assets
Total	43,708	56,696
Equity Securities | non-U.S.
Fair values of pension plan assets
Total	819	11,028
Equity Funds
Fair values of pension plan assets
Total	28,052	17,522
Equity Funds | U.S.
Fair values of pension plan assets
Total		26,903
Equity Funds | non-U.S.
Fair values of pension plan assets
Total	0	26,903
Equity Funds | International LP
Fair values of pension plan assets
Total		17,522
Bond funds - government
Fair values of pension plan assets
Total	22,237	47,800
Bond funds - other
Fair values of pension plan assets
Total	150,712	69,617
Real estate
Fair values of pension plan assets
Total	3,812	10,006
Cash and Cash Equivalents
Fair values of pension plan assets
Total	7,823	7,417
Partnership
Fair values of pension plan assets
Total	12,862	13,360
Long/short equity-focused hedge funds
Fair values of pension plan assets
Total	0	5,255
International hedge funds
Fair values of pension plan assets
Total	23,542	25,191
Quoted Prices in Active Markets (Level 1)
Fair values of pension plan assets
Total	52,350	75,141
Quoted Prices in Active Markets (Level 1) | Equity Securities | U.S.
Fair values of pension plan assets
Total	43,708	56,696
Quoted Prices in Active Markets (Level 1) | Equity Securities | non-U.S.
Fair values of pension plan assets
Total	819	11,028
Quoted Prices in Active Markets (Level 1) | Cash and Cash Equivalents
Fair values of pension plan assets
Total	7,823	7,417
Significant Other Observable Inputs (Level 2)
Fair values of pension plan assets
Total	201,001	161,842
Significant Other Observable Inputs (Level 2) | Equity Securities | non-U.S.
Fair values of pension plan assets
Total	0	0
Significant Other Observable Inputs (Level 2) | Equity Funds
Fair values of pension plan assets
Total	28,052
Significant Other Observable Inputs (Level 2) | Equity Funds | U.S.
Fair values of pension plan assets
Total		26,903
Significant Other Observable Inputs (Level 2) | Equity Funds | non-U.S.
Fair values of pension plan assets
Total	0
Significant Other Observable Inputs (Level 2) | Equity Funds | International LP
Fair values of pension plan assets
Total		17,522
Significant Other Observable Inputs (Level 2) | Bond funds - government
Fair values of pension plan assets
Total	22,237	47,800
Significant Other Observable Inputs (Level 2) | Bond funds - other
Fair values of pension plan assets
Total	150,712	69,617
Significant Other Observable Inputs (Level 2) | Real estate
Fair values of pension plan assets
Total	0	0
Significant Unobservable Inputs (Level 3)
Fair values of pension plan assets
Total	12,862	13,360
Significant Unobservable Inputs (Level 3) | Partnership
Fair values of pension plan assets
Total	12,862	13,360	$ 11,239
Significant Unobservable Inputs (Level 3) | Long/short equity-focused hedge funds
Fair values of pension plan assets
Total		0
Significant Unobservable Inputs (Level 3) | International hedge funds
Fair values of pension plan assets
Total	0	0
Significant Unobservable Inputs (Level 3) | Fixed Annuities
Fair values of pension plan assets
Total	0	0	$ 12,475
Not Leveled [Member]
Fair values of pension plan assets
Total	27,354	40,452
Not Leveled [Member] | Real estate
Fair values of pension plan assets
Total	3,812	10,006
Not Leveled [Member] | Long/short equity-focused hedge funds
Fair values of pension plan assets
Total		5,255
Not Leveled [Member] | International hedge funds
Fair values of pension plan assets
Total	$ 23,542	$ 25,191