Long-Term Obligations (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Summary of long-term obligations
Senior term notes	$ 573,984	$ 493,750
Total debt obligations	574,330	494,618
Capital lease obligations	44,523	32,418
Long term debt including capital lease obligation	618,853	527,036
Less - current portion	(32,571)	(28,101)
Long term debt and capital lease obligations	586,282	498,935
LIBOR + 1.75% or 2.0% at December 31, 2011
Summary of long-term obligations
Senior term notes	573,984	0
LIBOR + 2.25% or 2.5% at December 31, 2010
Summary of long-term obligations
Senior term notes	0	493,750
Revolving Credit Facility Due 2016 [Member]
Summary of long-term obligations
Revolving credit	0	0
Secured Seller Notes Due 2013 [Member]
Summary of long-term obligations
Secured seller notes	$ 346	$ 868