Operating Leases (Rent Expense) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property Subject to or Available for Operating Lease [Line Items]
Rent expense	$ 125,579	$ 119,674	$ 114,394
Leased Facilities [Member]
Property Subject to or Available for Operating Lease [Line Items]
Rent expense	96,540	95,808	92,854
Leased Vehicles [Member]
Property Subject to or Available for Operating Lease [Line Items]
Rent expense	$ 29,039	$ 23,866	$ 21,540