Retirement Plans - Summary of Fair Values of Pension Plan (Details 8) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair values of pension plan assets
Total fair value of plan assets	$ 293,567	$ 290,795
Equity Securities | U.S.
Fair values of pension plan assets
Total fair value of plan assets	43,708	56,696
Equity Securities | non-U.S.
Fair values of pension plan assets
Total fair value of plan assets	819	11,028
Equity Funds
Fair values of pension plan assets
Total fair value of plan assets	28,052	17,522
Equity Funds | U.S.
Fair values of pension plan assets
Total fair value of plan assets		26,903
Equity Funds | non-U.S.
Fair values of pension plan assets
Total fair value of plan assets	0	26,903
Equity Funds | International LP
Fair values of pension plan assets
Total fair value of plan assets		17,522
Bond funds - government
Fair values of pension plan assets
Total fair value of plan assets	22,237	47,800
Bond funds - other
Fair values of pension plan assets
Total fair value of plan assets	150,712	69,617
Real estate
Fair values of pension plan assets
Total fair value of plan assets	3,812	10,006
Cash and Cash Equivalents
Fair values of pension plan assets
Total fair value of plan assets	7,823	7,417
Partnership
Fair values of pension plan assets
Total fair value of plan assets	12,862	13,360
Long/short equity-focused hedge funds
Fair values of pension plan assets
Total fair value of plan assets	0	5,255
International hedge funds
Fair values of pension plan assets
Total fair value of plan assets	$ 23,542	$ 25,191