Earnings Per Share - Anti-dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted weighted average common shares outstanding (in shares)	229,294	258,917	197,350
Restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted weighted average common shares outstanding (in shares)	0	129	0
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted weighted average common shares outstanding (in shares)	148,175	188,050	25,640
Common stock subject to repurchase
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted weighted average common shares outstanding (in shares)	957	13,281	29,835