Quarterly report pursuant to Section 13 or 15(d)

Long-Term Debt - Schedule of Long-Term Debt (Parenthetical) (Detail)

v3.8.0.1
Long-Term Debt - Schedule of Long-Term Debt (Parenthetical) (Detail)
1 Months Ended 3 Months Ended
Mar. 31, 2018
Feb. 28, 2014
Mar. 31, 2018
2.000% Convertible Senior Notes Due 2019 [Member]      
Debt Instrument [Line Items]      
Convertible notes, interest rate 2.00% 2.00% 2.00%
Convertible notes maturity   Aug. 15, 2019 Aug. 15, 2019
2.625% Convertible Senior Notes Due 2024 [Member]      
Debt Instrument [Line Items]      
Convertible notes, interest rate 2.625%   2.625%
Convertible notes maturity Mar. 15, 2024   Mar. 15, 2024