Earnings Per Share - Summary of Anti-dilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential shares of common stock excluded from the computation of diluted earnings per share	1,391	437	1,559	875
RSUs & PSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential shares of common stock excluded from the computation of diluted earnings per share	592	437	446	399
ESPP purchase rights
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential shares of common stock excluded from the computation of diluted earnings per share	799	0	1,113	476