Subsequent Event (Details) - Subsequent Event [Member] $ in Millions	May 22, 2018 USD ($)
Sparta Fraud Claim Gain Contingency | Positive Outcome of Litigation
Subsequent Event [Line Items]
Gain Contingency, Unrecorded Amount	$ 4.7
Sparta Professional Negligence Claim Gain Contingency [Member] | Positive Outcome of Litigation
Subsequent Event [Line Items]
Gain Contingency, Unrecorded Amount	16.3
Sparta Implied Covenant Counterclaim Loss Contingency [Member]
Subsequent Event [Line Items]
Loss Contingency, Estimate of Possible Loss	$ 4.9