Stockholders' Equity - Common Stock and Preferred Stock (Details)	12 Months Ended
	Dec. 31, 2018 class_of_stock $ / shares shares	Dec. 31, 2017 $ / shares shares
Equity [Abstract]
Number of classes of stock | class_of_stock	2
Common stock, par value (in dollars per share) | $ / shares	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000