CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2015	Dec. 31, 2014
Consolidated Balance Sheets
Convertible senior notes, interest rate (as a percent)	2.50%	2.50%
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	117,500,000	58,750,000
Common stock, shares issued	30,868,011	25,599,550
Common stock, shares outstanding	30,868,011	25,599,550