Fair Value Measurements - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended
	Jul. 18, 2013	Mar. 31, 2015	Dec. 31, 2014	Jul. 18, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying amount of senior notes		$ 224,065,000	224,035,000
Other Asset Class [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value on recurring basis		0
6.625% senior notes due 2021 [Member] | Senior notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate	6.625%	6.625%	6.625%	6.625%
Due date	Jul. 15, 2021	Jul. 15, 2021	Jul. 15, 2021
Carrying amount of senior notes		224,065,000
Estimated fair value of senior notes		$ 157,500,000