Stockholders' Equity and Employee Benefit Plans - Common Stock and Preferred Stock - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Class Of Stock [Line Items]
Common stock, shares authorized	800,000,000		800,000,000
Common stock, par value	$ 0.00001		$ 0.00001
Preferred stock, shares authorized	100,000,000		100,000,000
Preferred stock, par value	$ 0.00001		$ 0.00001
Common Stock
Class Of Stock [Line Items]
Stock repurchased during period, shares	1,159	11,791
Stock repurchased during period, value	$ 16,000	$ 144,000
Stock repurchased, price per share	$ 13.65	$ 12.21
Maximum
Class Of Stock [Line Items]
Shares authorized for issuance	900,000,000