New Accounting Standards - Summary of Adjustments to Quarterly Data Resulting from Adoption of New Standard in Statements of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016
New Accounting Pronouncement Early Adoption [Line Items]
Income tax benefit	$ (71,992)	$ (13,705)		$ 98,054	$ (185,169)
Net loss	$ (127,700)	$ (41,971)		$ 111,961	$ (360,679)
Basic earnings per share	$ (0.52)	$ (0.23)		$ 0.45	$ (2.10)
Diluted earnings per share	$ (0.52)	$ (0.23)		$ 0.45	$ (2.10)
Accounting Standards Update 2016-09
New Accounting Pronouncement Early Adoption [Line Items]
Income tax benefit			$ (41,976)
Net loss			$ (93,772)
Basic earnings per share			$ (0.56)
Diluted earnings per share			$ (0.56)
Accounting Standards Update 2016-09 | As Reported
New Accounting Pronouncement Early Adoption [Line Items]
Income tax benefit			$ (44,038)
Net loss			$ (91,710)
Basic earnings per share			$ (0.55)
Diluted earnings per share			$ (0.55)