Revenue Recognition - Contract Acquisition Costs (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Contract Acquisition Costs
Expected amortization period, when the Company utilizes the practical expedient and expenses the costs as incurred	true
Amortization of contract acquisition cost	$ 0.3
Prepayments and other current assets
Contract Acquisition Costs
Current contract acquisition costs	1.1
Other assets
Contract Acquisition Costs
Long term contract acquisition costs	$ 0.8
Minimum
Contract Acquisition Costs
Amortization period	2 years
Maximum
Contract Acquisition Costs
Amortization period	6 years