Lease Obligations (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Leases [Abstract]
Operating Leases, Future Minimum Payments Due, Current	$ 38,671,000
Operating Leases, Future Minimum Payments, Due in Two Years	33,893,000
Operating Leases, Future Minimum Payments, Due in Three Years	29,924,000
Operating Leases, Future Minimum Payments, Due in Four Years	25,038,000
Operating Leases, Future Minimum Payments, Due Thereafter	187,349,000
Operating Leases, Rent Expense	$ 38,179,000	$ 33,003,000	$ 29,936,000