Acquisitions (Details) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended
	Oct. 02, 2012	Sep. 30, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 02, 2012
Fair value of the final consideration transferred
Stock consideration					$ 140,726,000
Merger costs related to the Credit Agreement, recognized as discount to borrowings			2,300,000
Central
Acquisitions
Interest acquired (as a percent)	100.00%					100.00%
Common stock issued (in shares)	6,161,332
Assumption of debt, net of cash acquired	217,675,000					217,675,000
Period after which contingent cash consideration to be paid	3 years
Price of share at which former stockholders of acquiree can elect to pay applicable amount (in dollars per share)	$ 23.64					$ 23.64
Minimum cash consideration to cover capped indemnities	17,000					17,000
Settlement reducing cash consideration
Cash consideration payable in three years	27,000,000	27,000,000				27,000,000
Period in which reduction in cash consideration payable for the seller's indemnification made		3 years
Indemnification of cost pursuant to merger agreement			80.00%
Central Net Debt Working Capital as defined in the Merger Agreement		(296,652,000)
Threshold		285,000,000
Excess over the threshold		(11,652,000)
Indemnification of certain defined adverse consequences, net		(14,541,000)
Reduction of cash consideration payable		14,541,000
Fair value of the final consideration transferred
Acquisition and integration related costs included in general and administrative expenses			8,541,000	10,918,000	28,036,000
Merger costs related to obtaining the Credit Agreement			1,303,000
Central | Total Fair Value
Settlement reducing cash consideration
Present value of cash consideration to be issued				807,000
Fair value of the final consideration transferred
Present value of cash consideration to be issued				$ 807,000