Schedule of Debt Obligations (Detail) - USD ($) $ in Thousands		Sep. 30, 2018		Dec. 31, 2017
Debt Instrument [Line Items]
Total debt		$ 697,147
Unamortized debt issuance costs		(5,509)		$ (7,406)
Total debt	[1]	691,638		800,842
Less current maturities		50,406		44,349
Total long-term debt		641,232		756,493
Senior Secured Notes
Debt Instrument [Line Items]
Total debt		376,154		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]	55,878
Total debt		111,000
Variable Funding Notes
Debt Instrument [Line Items]
Total debt		94,250	[4]	91,363
Senior Secured Term Loan
Debt Instrument [Line Items]
Total debt		170,865		74,813
Less current maturities		$ 7,700		$ 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 September 30, 2018. The actual principal outstanding balance of the 5.75% Convertible Notes is $111.0 million as of September 30, 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 September 30, 2018. The actual principal outstanding balance of the Variable Funding Notes is $100.0 million as of September 30, 2018.