Senior Secured Notes - Additional Information (Detail) - USD ($)		1 Months Ended	12 Months Ended
	Oct. 05, 2015	Nov. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]
Cash paid for interest			$ 20,225,000	$ 17,445,000	$ 17,590,000
Loss on extinguishment of debt			14,079,000	0	0
Write-off of unamortized issuance costs			$ 1,579,000	$ 0	$ 0
Percentage of repurchase of notes on principal amount of notes			101.00%
Percentage of repurchase of notes on principal amount of notes upon sale of assets			100.00%
Senior Secured Notes principal amount			$ 250,000,000
7.75% Senior Secured Notes Due October 2020 [Member]
Line of Credit Facility [Line Items]
Senior secured notes, interest rate			7.75%
Senior Notes [Member] | 7.75% Senior Secured Notes Due October 2020 [Member]
Line of Credit Facility [Line Items]
Senior secured notes, issued	$ 250,000,000
Senior secured notes, interest rate	7.75%		7.75%
Senior secured notes, maturity date			Oct. 05, 2020
Frequency of payment			Quarterly
Date of first repayment			Oct. 15, 2015
Issuance costs	$ 8,900,000
Debt discount on transaction and facility fees	8,300,000
Direct debt issuance costs capitalized	400,000
Additional issuance costs	200,000
Debt instrument term			5 years
Senior secured notes, cash received	$ 100,300,000
Minimum cash and investments in marketable securities to be maintained			$ 60,000,000
Restricted cash to be maintained until release of 12% Notes liens		$ 50,000,000
Senior Notes [Member] | 12% Senior Secured Notes Due July 2017 [Member]
Line of Credit Facility [Line Items]
Senior secured notes, interest rate	12.00%
Senior secured notes, maturity date	Jul. 15, 2017
Repayment of senior secured notes	$ 125,000,000
Accrued interest paid on 12% notes at redemption	3,300,000
Redemption premium	12,500,000		11,300,000
Cash paid for interest	1,200,000		1,200,000
Loss on extinguishment of debt			$ 14,100,000
Write-off of unamortized issuance costs	$ 1,600,000