Stock Incentive Plans (Summary of Restricted Common Stock and Performance-Based Restricted Stock Unit Activity) (Details) - 6 months ended Jun. 30, 2015 - $ / shares	Total
Restricted Common Stock
Number of Shares
Unvested at the beginning of the period (in shares)	752,701
Granted (in shares)	426,552
Vested (in shares)	(4,000)
Forfeited (in shares)	(50,294)
Unvested at the end of the period (in shares)	1,124,959
Weighted Average Grant Date Fair Value
Unvested at the beginning of the period (in dollars per share)	$ 11.90
Granted (in dollars per share)	13.04
Vested (in dollars per share)	(8.95)
Forfeited (in dollars per share)	(11.59)
Unvested at the end of the period (in dollars per share)	$ 12.36
Restricted Stock Units
Number of Shares
Unvested at the beginning of the period (in shares)	776,500
Granted (in shares)	409,800
Forfeited (in shares)	(46,900)
Unvested at the end of the period (in shares)	1,139,400
Weighted Average Grant Date Fair Value
Unvested at the beginning of the period (in dollars per share)	$ 10.66
Granted (in dollars per share)	12.64
Forfeited (in dollars per share)	(10.92)
Unvested at the end of the period (in dollars per share)	$ 11.36