Bradley Agreement - Deficiency Payments, Net of Reimbursements (Details) $ in Millions	6 Months Ended
Jun. 30, 2018 USD ($)
Gain Contingency [Roll Forward]
Balance at the beginning of the year	$ 7.8
Deficiency payments made	0.1
Deficiency repayments received	(2.1)
Balance at the beginning of the year	$ 5.8

The amount or range of possible amounts of gain that could be realized upon the resolution of a contingency.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6397426&loc=d3e17499-108355

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