Schedule of Debt Obligations (Detail) - USD ($) $ in Thousands		Mar. 31, 2018		Dec. 31, 2017
Debt Instrument [Line Items]
Total debt		$ 769,722
Unamortized debt issuance costs		(7,062)		$ (7,406)
Total debt	[1]	762,660		800,842
Less current maturities		46,549		44,349
Total long-term debt		716,111		756,493
Senior Secured Notes
Debt Instrument [Line Items]
Total debt		397,500		408,174
Less current maturities		42,700		42,700
Convertible Notes | 1.50% Senior Subordinated Notes Due March 15, 2018
Debt Instrument [Line Items]
Total debt				233,898
Convertible Notes | 5.75% Senior Subordinated Notes Due August 2023
Debt Instrument [Line Items]
Total debt	[2],[3]	109,455
Total debt		116,200
Variable Funding Notes
Debt Instrument [Line Items]
Total debt		92,294	[4]	91,363
Senior Secured Term Loan
Debt Instrument [Line Items]
Total debt		170,473		74,813
Less current maturities		$ 3,900		$ 1,700

[1] Carrying amounts include aggregate unamortized debt discount and debt issuance costs.

[2] On February 12, 2018, the Company entered into the Exchange Agreements and consummated the Note Exchange on February 22, 2018, pursuant to which the Company exchanged approximately $125.0 million aggregate principal amount of its 1.50% Convertible Notes for 5.75% Convertible Notes issued by the Company in an aggregate principal amount of approximately $125.0 million. See below for further details.

[3] Reflects the debt carrying amount which is accounted for under the Fair Value Option in the unaudited condensed consolidated balance sheet as of March 31, 2018. The actual principal outstanding balance of the 5.75% Convertible Notes is $116.2 million as of March 31, 2018.

[4] Reflects the net debt carrying amount, effected by the outstanding balance of the original issue discount, in the unaudited condensed consolidated balance sheet as of March 31, 2018. The actual principal outstanding balance of the Variable Funding Notes is $100.0 million as of March 31, 2018.