Schedule of Debt Obligations (Detail) - USD ($) $ in Thousands		Mar. 31, 2019		Dec. 31, 2018
Debt Instrument [Line Items]
Total debt		$ 652,039
Unamortized debt issuance costs		(3,981)		$ (4,738)
Total debt	[1]	648,058		675,229
Less current maturities		61,391		54,263
Total long-term debt		586,667		620,966
Senior Secured Notes
Debt Instrument [Line Items]
Total debt		358,079		365,481
Less current maturities		46,000		46,000
Variable Funding Notes
Debt Instrument [Line Items]
Total debt		96,298	[2]	95,273
Senior Secured Term Loan
Debt Instrument [Line Items]
Total debt		171,355		171,137
Less current maturities		15,400		11,600
Convertible Notes | 5.75% Senior Subordinated Notes Due August 2023
Debt Instrument [Line Items]
Total debt		26,307	[3]	48,076
Total debt		$ 105,700		$ 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 March 31, 2019. The actual principal outstanding balance of the Variable Funding Notes is $100.0 million as of March 31, 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 March 31, 2019. The actual principal outstanding balance of the 5.75% Convertible Notes is $105.7 million as of March 31, 2019.