Defined Benefit Pension Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Service cost	$ 167	$ (208)	$ 825	$ 1,224
Interest cost	6,726	8,187	23,298	24,459
Expected return on assets	(8,024)	(10,604)	(28,782)	(31,428)
Amortization of actuarial loss	2,911	3,396	9,729	9,660
Net periodic benefit cost	$ 1,780	$ 771	$ 5,070	$ 3,915