Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Treasury stock, shares	1,563,607	132,142
Voting Common Stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	240,000,000	240,000,000
Common stock, shares issued	73,270,735	72,907,827
Common stock, shares outstanding	73,105,395	72,775,685