Convertible Notes, Net - Additional Information (Detail) - USD ($)	1 Months Ended		6 Months Ended
	May 31, 2017	Nov. 30, 2013	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Accrued interest payable			$ 11,690,000	$ 9,049,000
5.25% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Description of Convertible Notes conversion			The Convertible Notes are convertible at the holders' option into shares of our class A common stock, only under specific circumstances, prior to the close of business on August 31, 2018 and January 31, 2022, for the November 2013 and May 2017 convertible notes, respectively, at the applicable conversion rate in effect on the conversion date.
Debt instrument, conversion price			$ 31.60
Discount upon issuance of Convertible Notes		$ 9,100,000
Debt issuance costs		$ 4,100,000
Convertible Notes, assumed effective interest rate		6.50%
Convertible Senior Notes, Interest rate including amortization of discount upon issuance		7.16%
Accrued interest payable			$ 2,700,000	$ 755,000
4.38% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Discount upon issuance of Convertible Notes	$ 868,000,000,000
Debt issuance costs	$ 7,000,000
Convertible Notes, assumed effective interest rate	4.67%
Convertible Senior Notes, Interest rate including amortization of discount upon issuance	5.00%