Cost of Contracts, net - Future Amoritization and Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Expected future amortization of cost of contracts
2016	$ 3.2
2017	3.0
2018	2.5
2019	1.6
2020	0.6
2021 and Thereafter	1.0
Cost of contracts, net	11.9	$ 10.5
Amortization expense, cost of contracts	$ 3.1	$ 3.2	$ 2.8
Weighted average useful life	9 years	9 years 6 months	9 years 7 months 6 days