Derivative Financial Instruments (Effect Of Cash Flow Hedges On Financial Statements) (Details) - Forward Starting Pay Fixed Swaps [Member] - Cash Flow Hedging [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Effective Portion Pretax Hedge Loss Recognized in Other Comprehensive Income (Loss)	$ (140.1)	$ (75.2)	$ 0.0
Effective Portion Hedge Loss Reclassified from Accumulated Other Comprehensive Loss	(5.8)	(5.5)	(5.0)
Net realized gains on financial instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Ineffective Portion Hedge Loss Recognized	$ (7.7)	$ 0.0	$ 0.0