Benefit Plans and Other Postretirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Components of net periodic benefit cost:
Contributions to U.S defined contribution plans by the Company, maximum percentage of eligible compensation	5.00%
Matching contributions to U.S defined contribution plans by the Company	$ 941	$ 830
Pension Benefits
Components of net periodic benefit cost:
Service cost	2,046	2,112
Interest cost	6,017	5,207
Expected return on plan assets	(7,133)	(6,203)
Amortization of transition obligation	(24)	(27)
Amortization of prior service cost	673	495
Amortization of net actuarial losses	4,013	5,905
Net pension expense	5,592	7,489
U.S. plans, Pension Benefits
Components of net periodic benefit cost:
Estimated cash contribution to the Plans in 2014 based on current actuarial calculations	20,000
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	28	40
Interest cost	123	127
Amortization of net actuarial losses	105	193
Net pension expense	$ 256	$ 360