Fair Value Of Assets And Liabilities (Narrative) (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) contract	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) contract	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) on derivative	$ 6.6	$ 8.4	$ 9.1	$ 7.8
Number of futures contracts (as shown) | contract	10		10		15
Fair Value Inputs, Discount Rate			3.33%
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets under Management, Assumed Growth Rate			0.69%
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets under Management, Assumed Growth Rate			6.67%
Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets under Management, Assumed Growth Rate			3.41%
Future [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional value of futures contracts	$ 1.7		$ 1.7		$ 1.9
Designated as Hedging Instrument [Member] | Foreign Exchange Option [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Put option contracts, purchases	$ 0.0	$ 7.0