Benefit Plans and Other Postretirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Components of net periodic benefit cost:
Contributions to U.S defined contribution plans by the Company, maximum percentage of eligible compensation (as a percent)	5.00%
Matching contributions to U.S defined contribution plans by the Company	$ 830	$ 725
Pension Benefits
Defined Benefit Plan Disclosure
Number of U.S. defined benefit pension plans	2
Components of net periodic benefit cost:
Service cost	2,112	1,945
Interest cost	5,207	5,527
Expected return on plan assets	(6,203)	(6,236)
Amortization of transition obligation	(27)	(27)
Amortization of prior service cost	495	541
Amortization of net actuarial losses	5,905	4,553
Net pension expense	7,489	6,303
U.S. plans, Pension Benefits
Components of net periodic benefit cost:
Estimated cash contribution to the Plans in 2013 based on current actuarial calculations	21,000
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	40	45
Interest cost	127	169
Amortization of transition obligation		16
Amortization of net actuarial losses	193	242
Net pension expense	$ 360	$ 472