Equity Compensation Plans - Restricted Stock and RSUs (Details) - Restricted stock and restricted stock units - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Equity Compensation Plans
Vesting period	3 years
Changes in unvested awards
Nonvested at the beginning of the period (in shares)	409,000
Granted (in shares)	158,500	120,000
Vested (in shares)	(91,500)
Forfeited (in shares)	(1,000)
Nonvested at the end of the period (in shares)	475,000
Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 5.89
Granted (in dollars per share)	11.02
Vested (in dollars per share)	5.07
Forfeited (in dollars per share)	5.38
Nonvested at the end of the period (in dollars per share)	$ 7.76
Additional information
Total unrecognized compensation cost of restricted awards	$ 2.3	$ 1.2
Expected weighted-average period for recognition of unrecognized compensation	2 years 3 months 22 days	2 years 1 month 28 days