Long-Term Debt - Additional information (Detail) (USD $)	3 Months Ended											0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 6.6% Senior Notes, Due 2018	Mar. 31, 2014 Including Acquisition Bridge Debt	Mar. 31, 2014 Excluding Acquisition Bridge Debt	Mar. 31, 2014 Minimum	Mar. 31, 2014 Revolving Facility	Dec. 31, 2013 Revolving Facility	Mar. 31, 2013 Revolving Facility	Mar. 31, 2014 Trade Receivable Credit Facility	Dec. 31, 2013 Trade Receivable Credit Facility	Apr. 18, 2014 Trade Receivable Credit Facility Subsequent Event	Mar. 31, 2014 Term Loan Facility
Debt Instrument
Credit facility commitment							$ 350,000,000			$ 150,000,000			$ 250,000,000
Outstanding borrowing under credit facility										232,566,000	234,101,000
Credit facility, maturity date												Sep. 30, 2014
Senior unsecured revolving facility, maturity period							5 years
Debt covenant				3.50x	3.75x
Reduction of consolidated debt in the debt ratio calculation						50,000,000
Maximum consolidated debt reduction for unrestricted cash and cash equivalents for debt covenant calculation	200,000,000
Outstanding letters of credit							2,507,000	2,507,000	2,507,000
Additional interest expense	288,000	269,000
Increase in annual interest expense due to ongoing amortization of the terminated value of the swap agreements			$ 1,200,000