Commitments and Contingencies Commitments and Contingencies (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Total Costs to Remediate IRC Section 7702 and 72(s) Issues [Member]
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period			$ 12.8
Toll Charges and Fees to Remediate IRC Section 7702 and 72(s) Issues [Member] [Member]
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period		$ 14.6	12.6
Cost of Additional Reserve Liabilities to Remediate IRC Section 7702 Issue
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period			0.3
Increase in Toll Charges and Fees to Remediate IRC Section 7702 and 72(s) Issues During the Period[Member] [Member] [Member]
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period			2.1
Additional General Expenses to Remediate IRC Section 7702 and 72(s) Issues [Member] [Member] [Member]
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period			1.4	$ 2.0
Minimum [Member] | Cost Range to Remediate IRC Section 7702 and 72(s) Issues [Member]
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period			6.1
Minimum [Member] | Additional General Expenses to Remediate IRC Section 7702 and 72(s) Issues [Member] [Member] [Member]
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period	$ 0.5
Maximum [Member] | Cost Range to Remediate IRC Section 7702 and 72(s) Issues [Member]
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period			$ 40.5
Maximum [Member] | Additional General Expenses to Remediate IRC Section 7702 and 72(s) Issues [Member] [Member] [Member]
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period	$ 1.0