Benefit Plans and Other Postretirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Plan	Jun. 30, 2011
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			$ 1,400	$ 1,300
Pension Benefits
Defined Benefit Plan Disclosure
Number of U.S. defined benefit pension plans			2
Components of net periodic benefit cost:
Service cost	1,939	1,354	3,884	2,967
Interest cost	5,426	4,587	10,953	10,391
Expected return on plan assets	(6,083)	(4,415)	(12,319)	(10,453)
Amortization of transition obligation	(27)	(29)	(54)	(56)
Amortization of prior service cost	534	412	1,075	990
Amortization of net actuarial losses	4,555	2,456	9,108	5,890
Net pension expense	6,344	4,365	12,647	9,729
U.S. plans, Pension Benefits
Components of net periodic benefit cost:
Employer contributions	4,100		12,900
Estimated cash contribution to the Plans in 2012 based on current actuarial calculations	26,000		26,000
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	45	45	90	100
Interest cost	169	201	339	424
Amortization of transition obligation	16	16	31	31
Amortization of net actuarial losses	242	311	483	651
Net pension expense	$ 472	$ 573	$ 943	$ 1,206