Common Stock and Incentive Awards - Summary of ERI Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2014	Sep. 19, 2014	Dec. 31, 2016	Dec. 31, 2015
Options
Outstanding at the beginning of the Period (in shares)	474,833		312,200	398,200
Exercised - in shares	(76,633)		(132,900)	0
Outstanding at the end of the Period (in shares)	398,200	474,833	169,300	312,200
Expired (in shares)			(10,000)	(86,000)
Range of Exercise Price
Lower end of exercise price	$ 2.44	$ 2.44	$ 2.44	$ 2.44
Upper end of exercise price	16.27	16.27	16.27	16.27
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	7.13		6.94	7.88
Exercised (in dollars per share)	3.22		2.89
Outstanding at the end of the period (in dollars per share)	$ 7.88	$ 7.13	9.94	6.94
Expired (in dollars per share)			$ 11.30	$ 11.30
Weighted‑ Average Remaining Contractual Life
Weighted- Average Remaining Contractual Life (in years)	4 years 6 months 15 days		10 months 10 days	3 years 5 months 19 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 0.2		$ 1.2	$ 1.3
Exercised
Range of Exercise Price
Lower end of exercise price	$ 2.44		$ 2.44
Upper end of exercise price	$ 3.94		3.94
Expired
Range of Exercise Price
Upper end of exercise price			$ 11.30	$ 11.30