Commitments and Contingencies - Purchase Commitments (Details) $ in Millions	Dec. 31, 2017 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Purchase obligation, due in next twelve months	$ 9.6
Purchase obligation, due in second and third year	10.0
Purchase obligation, due in fourth and fifth year	0.7
Purchase obligation	$ 20.3

Minimum amount of purchase arrangement maturing in the fourth and fifth fiscal years following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

No definition available.

Name:	us-gaap_PurchaseObligationDueInFourthAndFifthYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant