Common Stock - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended		6 Months Ended
	Apr. 26, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2017	Jun. 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				$ 1,412,286	$ 578,683
2018 Notes [Member] | Recourse debt [Member]
Overview Of The Company [Line Items]
Principal amount of convertible senior notes		$ 144,800		$ 144,800
Convertible instrument, shares issued		1,163,442
Increase to additional paid-in capital		$ 141,800
Convertible notes and warrants settled early, net payment recorded as an increase to additional paid-in capital		$ 43,600
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
Increase to additional paid-in capital	$ 10,300