Net Carrying Amount of Debt (Detail) - USD ($) $ in Thousands		Dec. 31, 2018		Dec. 31, 2017
Debt Instrument [Line Items]
Total debt		$ 679,967
Unamortized debt issuance costs		(4,738)		$ (7,406)
Total debt	[1]	675,229		800,842
Less current maturities		54,263		44,349
Total long-term debt		620,966		756,493
Senior Secured Notes
Debt Instrument [Line Items]
Total debt		365,481		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	[2]			233,898
Total debt				233,900
Convertible Notes | 5.75% Senior Subordinated Notes Due August 2023
Debt Instrument [Line Items]
Total debt	[2],[3]	48,076
Total debt		109,700
Variable Funding Notes
Debt Instrument [Line Items]
Total debt		95,273	[4]	91,363
Senior Secured Term Loan
Debt Instrument [Line Items]
Total debt		171,137		74,813
Less current maturities		$ 11,600		$ 1,700

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

[2] On February 22, 2018, the Company exchanged $125 million of aggregate principal amount of 1.50% Convertible Notes for $125 million of aggregate principal amount of 5.75% Convertible Notes. See below for further details.

[3] Reflects the debt carrying amount which is accounted for under the Fair Value Option in the consolidated balance sheet as of December 31, 2018. The actual principal outstanding balance of the 5.75% Convertible Notes is $109.7 million as of December 31, 2018.

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