Net Income (Loss) Per Share - Computation of Basic and Diluted Net Income (Loss) Per Share (Details) (USD $)
In Thousands, except Per Share data, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Earnings Per Share [Abstract]                      
Net income (loss) $ 11,245 $ 2,441 $ (2,575) $ (4,035) $ (1,056) $ 367 $ 1,059 $ 1,057 $ 7,076 $ 1,427 $ 3,379
Less: Undistributed earnings allocated to participating securities                 0 1,210 1,210
Less: Allocation of net income to participating preferred shares - basic                 0 74 749
Net income (loss) attributable to common stockholders - basic                 7,076 143 1,420
Weighted average shares outstanding used to compute basic net income (loss) per share                 50,564 33,744 33,008
Net income (loss) per share attributable to common stockholders - basic $ 0.18 $ 0.04 $ (0.05) $ (0.12) $ (0.03) $ 0.00 $ 0.01 $ 0.01 $ 0.14 $ 0.00 $ 0.04
Less: Allocation of net income to participating preferred shares - diluted                 0 67 664
Net income (loss) attributable to common stockholders - diluted                 $ 7,076 $ 150 $ 1,505
Stock awards                 8,528 5,877 6,392
Warrants                 0 31 31
Weighted average shares used to compute diluted net income (loss) per share                 59,092 39,652 39,431
Net income (loss) per share attributable to common stockholders - diluted $ 0.16 $ 0.03 $ (0.05) $ (0.12) $ (0.03) $ 0.00 $ 0.01 $ 0.01 $ 0.12 $ 0.00 $ 0.04