Lease Obligations (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Leases [Abstract]
Operating Leases, Future Minimum Payments Due, Current	$ 34,635,000
Operating Leases, Future Minimum Payments, Due in Two Years	31,177,000
Operating Leases, Future Minimum Payments, Due in Three Years	26,808,000
Operating Leases, Future Minimum Payments, Due in Four Years	22,646,000
Operating Leases, Future Minimum Payments, Due Thereafter	173,015,000
Operating Leases, Rent Expense	$ 33,003,000	$ 29,936,000	$ 28,067,000