Stockholders' Equity - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stockholders' Equity
Shares of common stock, authorized	600,000,000	600,000,000
Shares of common stock, issued and sold (in shares)	167,430,773	160,785,764
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred Stock, shares outstanding	0	0
Common stock
Stockholders' Equity
Common stock issued under employee stock plans (in shares)	6,645,009	11,276,672	9,154,487