Consolidated statements of changes in convertible preferred stock and stockholders' equity (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 14, 2012	Dec. 31, 2011	Dec. 31, 2010
Consolidated statements of changes in convertible preferred stock and stockholders' equity
Series A Convertible preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01		$ 0.01	$ 0.01
Series A Convertible preferred stock, shares authorized	10,000,000	10,000,000	10,000,000	4,000,000	4,000,000
Common stock par value (in dollars per share)	$ 0.01	$ 0.01		$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000	250,000,000	80,000,000	70,000,000