Lease Commitments (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Future annual minimum lease payments in operating leases
2013	$ 76,789,000
2014	69,271,000
2015	61,596,000
2016	49,623,000
2017	30,922,000
Thereafter	68,217,000
Total minimum lease payments	356,418,000
Total rent expense	$ 76,700,000	$ 70,600,000	$ 69,200,000