Investments In Unconsolidated Real Estate Entities (Investment in PSB) (Narrative) (Details) - PSB [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Common stock owned of PSB	7,158,354	7,158,354	7,158,354
Limited partnership units in PSB	7,305,355	7,305,355	7,305,355
Ownership interest, percentage	42.00%
Limited partnership units option to convert to common stock, conversion basis.	1
Closing price per share	$ 164.87
Market value	$ 2,400.0
Cash distribution received	60.7	$ 55.0	$ 49.2
Basis differential	4.2	7.4
Amortization of basis differential	$ 3.2	$ 1.8	$ 1.3