Fair Value Measurements - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) Company Lenders	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Fair Value Disclosures [Abstract]
Interest and dividends	$ 139	$ 103	$ 248	$ 171
Mark-to-market gain (loss)	(576)	$ 2,100	832	$ 2,600
Allowance for doubtful accounts on accounts receivable	2,961		$ 2,961		$ 2,719
Number of financial institutions included in counter parties | Company			17
Number of secured lenders not in banking credit facility | Lenders			2
Net derivative assets	$ 19,900		$ 19,900