Schedule of Debt Obligations (Detail) - USD ($) $ in Thousands		Jun. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total debt	[1]	$ 1,351,262	$ 1,449,392
Unamortized debt issuance costs	[2]	(23,890)	(15,016)
Less current maturities		76,123	61,123
Total long-term debt		1,275,139	1,388,269
Senior Secured Notes
Debt Instrument [Line Items]
Total debt		682,345	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	[3]	319,256	357,453
Convertible Notes | 2.50% Senior Subordinated Notes Due June 2016
Debt Instrument [Line Items]
Total debt	[4]		294,048
Variable Funding Notes
Debt Instrument [Line Items]
Total debt		100,000	$ 100,000
Senior Secured Term Loan
Debt Instrument [Line Items]
Total debt		$ 273,551

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

[2] During the first quarter of the year ending December 31, 2016, the Company retrospectively adopted ASU 2015-03, “Simplifying the Presentation of Debt Issuance Costs”. Refer to Note 16 for further details.

[3] In June 2016, the Company repurchased $51.7 million par value of the 1.50% Convertible Notes. See below for further details.

[4] In April 2016, the Company repurchased $143.9 million par value of the 2.50% Convertible Notes. Upon maturity of the notes on June 1, 2016, the Company repaid the remaining outstanding balance of $156.1 million in cash. See below for further details.