Schedule of Debt Obligations (Detail) - USD ($) $ in Thousands		Jun. 30, 2019		Dec. 31, 2018
Debt Instrument [Line Items]
Total debt		$ 645,365
Unamortized debt issuance costs		(3,224)		$ (4,738)
Total debt	[1]	642,141		675,229
Less current maturities		67,163		54,263
Total long-term debt		574,978		620,966
Senior Secured Notes
Debt Instrument [Line Items]
Total debt		353,163		365,481
Less current maturities		47,900		46,000
Variable Funding Notes
Debt Instrument [Line Items]
Total debt		97,364	[2]	95,273
Senior Secured Term Loan
Debt Instrument [Line Items]
Total debt		171,648		171,137
Less current maturities		19,300		11,600
Convertible Notes | 5.75% Senior Subordinated Notes Due August 2023
Debt Instrument [Line Items]
Total debt		23,190	[3]	48,076
Total debt		$ 94,600		$ 109,700

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

[2] 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 June 30, 2019. The actual principal outstanding balance of the Variable Funding Notes is $100.0 million as of June 30, 2019.

[3] Reflects the debt carrying amount which is accounted for under the Fair Value Option in the unaudited condensed consolidated balance sheet as of June 30, 2019. The actual principal outstanding balance of the 5.75% Convertible Notes is $94.6 million as of June 30, 2019.