Stock-Based Compensation - Non-vested Restricted Stock (Details) - Restricted stock unit awards - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restricted Stock Unit (RSU) Awards Outstanding
Aggregate grant date fair value of restricted stock unit awards outstanding	$ 7,763	$ 6,306	$ 4,438
Unrecognized compensation cost related to non-vested restricted stock unit awards	$ 5,995
Weighted-average period over which unrecognized compensation cost is expected to be recognized	3 years
Number of Restricted Stock Awards Outstanding
Non-vested restricted stock unit awards outstanding at the beginning of the year (in shares)	2,370,803
Restricted stock unit awards granted (In shares)	3,046,681
Restricted stock unit awards forfeited (in shares)	(831,290)
Restricted stock unit awards vested (in shares)	(835,902)
Non-vested restricted stock unit awards outstanding at the end of the year (in shares)	3,750,292	2,370,803
Weighted Average Grant Date Fair Value Per Share
Non-vested restricted stock unit awards outstanding at the beginning of the year (in dollars per shares)	$ 2.66
Restricted stock unit awards granted (in dollars per share)	1.81
Restricted stock unit awards forfeited (in dollars per share)	2.23
Restricted stock unit awards vested (in dollars per share)	2.32
Non-vested restricted stock unit awards outstanding at the end of the year (in dollars per shares)	$ 2.07	$ 2.66
Maximum
Restricted Stock Unit (RSU) Awards Outstanding
Vesting period	4 years