Fair Value Measurements (Fair Value Of Notes Payable) (Details) - USD ($) $ in Millions		Jun. 30, 2020		Dec. 31, 2019		Jun. 30, 2019
Carrying Value		$ 3,224.9		$ 2,524.1
Fixed rate notes payable
Carrying Value		3,125.1		2,380.4
Estimated Fair Value		3,455.3		2,533.5
Floating rate notes payable (1)
Carrying Value		99.8	[1]	143.7	[1]	$ 99.6
Estimated Fair Value	[1]	$ 99.0		$ 143.8

[1] Includes balances outstanding under our unsecured credit facility at December 31, 2019.