Benefit Plans and Other Postretirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 item	Jun. 30, 2012
Components of net periodic benefit cost:
Employer contributions	$ 4,000		$ 4,000
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			1,600	1,400
Pension Benefits
Defined Benefit Plan Disclosure
Number of U.S. defined benefit pension plans			2
Components of net periodic benefit cost:
Service cost	2,103	1,939	4,215	3,884
Interest cost	5,107	5,426	10,314	10,953
Expected return on plan assets	(6,071)	(6,083)	(12,274)	(12,319)
Amortization of transition obligation	(27)	(27)	(54)	(54)
Amortization of prior service cost	485	534	980	1,075
Amortization of net actuarial losses	5,897	4,555	11,802	9,108
Net pension expense	7,494	6,344	14,983	12,647
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		21,000
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	40	45	80	90
Interest cost	127	169	255	339
Amortization of transition obligation		16		31
Amortization of net actuarial losses	193	242	385	483
Net pension expense	$ 360	$ 472	$ 720	$ 943