Schedule of Debt Obligations (Detail) - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total debt	[1]	$ 1,443,245	$ 1,449,392
Unamortized debt issuance costs	[2]	(13,866)	(15,016)
Less current maturities		61,123	61,123
Total long-term debt		1,382,122	1,388,269
Senior Secured Notes
Debt Instrument [Line Items]
Total debt		697,626	712,907
Less current maturities		61,100	61,100
Convertible Notes | 1.50% Senior Subordinated Notes Due March 15, 2018
Debt Instrument [Line Items]
Total debt		361,873	357,453
Convertible Notes | 2.50% Senior Subordinated Notes Due June 2016
Debt Instrument [Line Items]
Total debt		297,612	294,048
Variable Funding Notes
Debt Instrument [Line Items]
Total debt		$ 100,000	$ 100,000

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

[2] During the Current Quarter, the Company retrospectively adopted ASU 2015-03, “Simplifying the Presentation of Debt Issuance Costs”. Refer to Note 16 for further details.