Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Total costs to remediate IRC Section 7702 issue	$ 14.4	$ 14.6
Toll charges and fees to remediate IRC Section 7702 issue	14.1
Cost of claim and reserve liabilities to remediate IRC Section 7702 issue	0.3
Increase in total cost to remediate Section 7702 and 72(s) issue during the period	(0.2)
Consulting fees to remediate IRC Section 7702 and 72(s) issue	1.9
Minimum [Member]
Loss Contingencies [Line Items]
Cost Range to Remediate IRC Section 7702 Issue	7.5
Minimum [Member] | IRC Section 7702 remediation costs [Member]
Loss Contingencies [Line Items]
Loss contingency, range of possible loss	1.0
Maximum [Member]
Loss Contingencies [Line Items]
Cost Range to Remediate IRC Section 7702 Issue	44.8
Maximum [Member] | IRC Section 7702 remediation costs [Member]
Loss Contingencies [Line Items]
Loss contingency, range of possible loss	$ 2.0