Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Changes in fair value of contingent consideration [Roll Forward]
Liability balance, beginning of period	$ 31,683
Accretion of present value discount	209
Liability balance, end of period	31,892
Other long-term liabilities [Abstract]
Multiemployer pension withdrawal liability	31,892
Level 1 [Member]
Other long-term liabilities [Abstract]
Multiemployer pension withdrawal liability	0
Level 2 [Member]
Other long-term liabilities [Abstract]
Multiemployer pension withdrawal liability	0
Level 3 [Member]
Other long-term liabilities [Abstract]
Multiemployer pension withdrawal liability	$ 31,892