Fair Value Measurements (Fair Value Of Notes Payable) (Details) - USD ($) $ in Millions		Mar. 31, 2020		Dec. 31, 2019		Mar. 31, 2019
Carrying Value		$ 2,606.9		$ 2,524.1
Fixed rate notes payable
Carrying Value		2,381.1		2,380.4
Estimated Fair Value		2,376.5		2,533.5
Floating rate notes payable (1)
Carrying Value		225.8	[1]	143.7	[1]	$ 341.6
Estimated Fair Value	[1]	$ 220.9		$ 143.8

[1] Includes balances outstanding under our unsecured credit facility at March 31, 2020 and December 31, 2019.