Stockholders' Equity - Narrative (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares of common stock, authorized (in shares)	600,000,000.0	600,000,000
Common stock, shares, outstanding (in shares)	189,461,000	180,175,000
Settlement of 2018 Notes conversion feature (in shares)		1,300,000
Preferred stock, shares authorized (in shares)	10,000,000.0	10,000,000
Preferred stock, shares outstanding (in shares)	0	0
Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Common stock issued under employee stock plans (in shares)	5,003,000	5,899,000	7,386,000
Settlement of 2018 Notes conversion feature (in shares)		(1,314,000)
2018 Warrants
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Number of shares to be issued upon exercise of the Warrants (in shares)	4,300,000