Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	240,000,000	240,000,000
Common stock, shares issued (in shares)	70,148,386	69,871,535
Common stock, shares outstanding (in shares)	68,455,011	68,269,567
Treasury stock (in shares)	1,693,375	1,601,968
Voting Common Stock, $0.0001 par value
Common stock, par value (in dollars per share)	$ 0.0001
Common stock, shares authorized (in shares)	240,000,000