Convertible Notes, Net - Additional Information (Detail) - USD ($)	1 Months Ended		9 Months Ended
	May 31, 2017	Nov. 30, 2013	Sep. 30, 2017	Sep. 29, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Convertible notes, net			$ 562,741,000		$ 166,762,000
Accrued interest payable			19,922,000		9,049,000
5.25% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Convertible Senior Notes, Principal amount			$ 172,500,000
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				$ 31.02
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			$ 9,000,000		$ 755,000
4.38% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Convertible Senior Notes, Principal amount			402,500,000
Discount upon issuance of Convertible Notes	$ 979,000
Debt issuance costs	$ 8,400,000
Convertible Notes, assumed effective interest rate	4.57%
Convertible Senior Notes, Interest rate including amortization of discount upon issuance	4.91%
May 2017 Convertible Notes [Member]
Debt Instrument [Line Items]
Convertible Senior Notes, Principal amount	$ 287,500,000		115,000,000
Convertible notes, net			$ 402,500,000