Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Commitments and Contingencies Disclosure [Abstract]
Lease expiration date, maximum	Dec. 31, 2020
Rent expense	$ 17,873	$ 17,524	$ 17,375
Minimum rentals for aggregate lease commitments
2014	8,398
2015	5,378
2016	3,129
2017	1,892
2018	778
Thereafter	311
Total	19,886
Aggregate residual value at lease expiration for vehicle leases	11,741
Guaranteed aggregate residual value at lease expiration for vehicle leases	7,659
Liability for the estimated end-of-term loss related to residual value guarantee	398
Louisville facility lease term	5 years
Future minimum payments due for Louisville facility lease	4,710
Term of unrecorded unconditional purchase obligation	three year
Minimum purchase obligation	2,102
Remaining minimum purchase obligation	$ 1,306