Fair Value Measurements (Fair Value Of Notes Payable) (Details) - USD ($) $ in Millions		Sep. 30, 2015		Dec. 31, 2014		Sep. 30, 2014
Carrying Value		$ 2,715.2		$ 2,743.5
Fixed rate notes payable
Carrying Value		2,283.7		2,533.8
Estimated Fair Value		2,380.3		2,666.1
Floating rate notes payable (1)
Carrying Value		431.5	[1]	209.7	[1]	$ 210.1
Estimated Fair Value	[1]	$ 423.6		$ 203.7

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