Contingencies - Multi-Employer Pension Plan (Details) - Multi-employer pension plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Multi-employer pension plan
Addition to accrued plan liability	$ 0.4
Payroll and benefits payable
Multi-employer pension plan
Accrued plan liability		$ 0.9	$ 0.9