Common Stock - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended		3 Months Ended	9 Months Ended
	Apr. 26, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Apr. 18, 2017
Overview Of The Company [Line Items]
Common stock shares issued			1,536,259
Issuance of common stock public offering			$ 399,600
Convertible notes and warrants settled early, net payment recorded as an increase to additional paid-in capital					$ 2,442,942	$ 1,678,475
2018 Notes [Member] | Convertibles and Bonds with Warrants Attached [Member]
Overview Of The Company [Line Items]
Convertible instrument, shares issued				17,433
Convertible instrument, shares received				169,890
2018 Notes [Member] | Recourse debt [Member]
Overview Of The Company [Line Items]
Principal amount of convertible senior notes		$ 144,800		$ 42,700	$ 42,700
Convertible instrument, shares issued		1,163,442		250,198
Increase to additional paid-in capital		$ 141,800		$ 9,300
Convertible notes and warrants settled early, net payment recorded as an increase to additional paid-in capital		$ 43,600
Convertible instrument exchanged for cash				32,700
2018 Notes [Member] | Recourse debt [Member] | Bond Hedges and Warrants [Member]
Overview Of The Company [Line Items]
Increase to additional paid-in capital				$ 6,300
Chief Executive Officer [Member]
Overview Of The Company [Line Items]
Common stock shares issued			95,420
Issuance of common stock public offering			$ 25,000
Chief Executive Officer [Member] | Zero-coupon Convertible Senior Notes due in 2020 [Member] | Recourse debt [Member]
Overview Of The Company [Line Items]
Principal amount of convertible senior notes							$ 10,000
Convertible instrument, shares issued	33,333,000
Increase to additional paid-in capital	$ 10,300