Commitments (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Present Value of Future Minimum Lease Payments, Sale Leaseback Transactions [Abstract]
OperatingleasesfutureminimumpaymentsThereafter	$ 47,115,000
Operatingleasesfutureminimumpayments2016	26,303,000
Operatingleasesfutureminimumpayments2015	34,120,000
Operatingleasesfutureminimumpayments2014	41,373,000
OperatingLeasesFutureMinimumPayments2013	45,479,000
Operating Leases, Future minimum payments 2012	48,538,000.0
Operating Leases, Future Minimum Payments Due, Current	242,928,000
Operating Leases, Rent Expense	58,600,000	53,900,000	40,900,000
Operating Leases, Income Statement, Sublease Revenue	$ 1,900,000	$ 1,200,000