Legal Proceedings Gain Contingencies (Details) - Positive Outcome of Litigation - Subsequent Event [Member] $ in Millions	May 22, 2018 USD ($)
Sparta Fraud Claim Gain Contingency
Gain Contingencies [Line Items]
Gain Contingency, Unrecorded Amount	$ 4.7
Sparta Professional Negligence Claim Gain Contingency
Gain Contingencies [Line Items]
Gain Contingency, Unrecorded Amount	$ 16.3

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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