Stock Incentive Plans - Summary of Restricted Common Stock and Performance-Based Restricted Stock Unit Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restricted Common Stock
Number of Shares/Units
Unvested at the beginning of year (in shares)	374,817
Granted (in shares)	685,872
Vested (in shares)	(323,010)
Forfeited (in shares)	(33,350)
Expired (in shares)	(65,000)
Unvested at the end of year (in shares)	639,329	374,817
Weighted Average Grant Date Fair Value
Unvested at the beginning of year (in dollars per share)	$ 12.68
Granted (in dollars per share)	15.06	$ 13.05	$ 12.58
Vested (in dollars per share)	(14.04)
Forfeited (in dollars per share)	(14.43)
Expired (in dollars per share)	(13.23)
Unvested at the end of year (in dollars per share)	$ 14.40	$ 12.68
Restricted Stock Units
Number of Shares/Units
Unvested at the beginning of year (in shares)	751,500
Granted (in shares)	0
Vested (in shares)	0
Forfeited (in shares)	(45,900)
Unvested at the end of year (in shares)	705,600	751,500
Weighted Average Grant Date Fair Value
Unvested at the beginning of year (in dollars per share)	$ 12.41
Granted (in dollars per share)	0.00
Vested (in dollars per share)	(0.00)
Forfeited (in dollars per share)	(12.39)
Unvested at the end of year (in dollars per share)	$ 12.41	$ 12.41