Employee Benefit Plan Obligations (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Employee Benefit Plan Obligations (Textual) [Abstract]
Company's expense for its defined contribution plans	$ 7,800,000	$ 5,300,000	$ 3,300,000
Adjustment of deferred tax assets associated with postretirement benefit		1,400,000
Accumulated benefit obligations related to the Company's defined benefit pension plans	110,000,000	90,400,000
Company contributed to the defined benefit pension plan to the next fiscal year	3,000,000
Contributions to the defined benefit pension plan	$ 5,000,000
Supplemental Employee Retirement Plan [Member]
Employee Benefit Plans [Line Items]
Calculated rate for the supplemental employee retirement plan	3.20%	4.20%	6.00%