Debt - Additional Information (Detail)		3 Months Ended		6 Months Ended
	Apr. 17, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	May 08, 2017	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Charge recognized as a result of redemption				$ 1,500,000	$ 0
Senior Secured Notes Due 2022 | Convertible Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount	$ 440,000,000
Interest rate	10.75%
Redemption price, percent of principal amount of notes redeemed	100.00%
Percent of notes with option to redeem	35.00%
Redemption price, percentage of principal amount	110.75%
Redemption price if required collateral coverage ratio not met, percentage of principal amount	100.00%
Minimum collateral coverage ratio	1.5
Collateral coverage ratio, amount added to cash and cash equivalents	4.75
Collateral coverage ratio, multiplier for Average Grantor EBITDA for seven most recent fiscal quarters	4
Period to redeem notes without default if required collateral coverage ratio not met	90 days
Redemption price if company experiences change of control, percent of principal amount	101.00%
Senior Notes Due 2017 | Convertible Senior Notes
Debt Instrument [Line Items]
Interest rate		6.25%		6.25%		6.25%
Charge recognized as a result of redemption		$ 1,500,000
Premium and expenses paid for redemption of debt		1,300,000
Write off of unamortized discount and fees related to the portion of the notes redeemed		200,000
Convertible Senior Notes Due 2021 | Convertible Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount		$ 213,500,000		$ 213,500,000			$ 213,500,000
Interest rate		5.50%		5.50%
Interest expense, debt		$ 4,700,000	$ 4,500,000	$ 9,400,000	5,200,000
Contractual interest coupon		2,900,000	2,900,000	5,900,000	3,400,000
Amortization of debt discount		1,500,000	1,300,000	2,900,000	1,500,000
Amortization of debt issuance costs		$ 300,000	$ 300,000	$ 600,000	$ 300,000