Stock-Based Compensation - Restricted Stock (Details) - Restricted Stock Units	3 Months Ended
	Mar. 31, 2016 $ / shares shares
Stock-based compensation
Vesting period for awards	3 years
Minimum age requirement of grantee as a condition for vesting	65 years
Units
Outstanding at the beginning of the period (in shares) | shares	550,009
Granted (in shares) | shares	384,572
Vested (in shares) | shares	(183,370)
Forfeited (in shares) | shares	(7,743)
Outstanding at the end of the period (in shares) | shares	743,468
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 24.60
Granted (in dollars per share) | $ / shares	12.72
Vested (in dollars per share) | $ / shares	13.83
Forfeited (in dollars per share) | $ / shares	30.16
Outstanding at the end of the period (in dollars per share) | $ / shares	$ 21.07