Fair Value Measurements (Fair Value Of Notes Payable) (Details) - USD ($) $ in Millions		Sep. 30, 2016		Dec. 31, 2015		Sep. 30, 2015
Carrying Value		$ 2,480.6		$ 2,724.7
Fixed rate notes payable
Carrying Value		2,274.5		2,273.3
Estimated Fair Value		2,419.3		2,358.8
Floating rate notes payable (1)
Carrying Value		206.1	[1]	451.4	[1]	$ 431.0
Estimated Fair Value	[1]	$ 199.7		$ 441.3

[1] Includes balances outstanding under our unsecured credit facility and unsecured short-term borrowings.