Dispositions and Real Property Held for Sale (Summary of Activity Related to Dispositions and Assets Held for Sale) (Details) - Disposal Group, Disposed of by Sale, Not Discontinued Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Total revenues	$ 449,080	$ 665,384	$ 769,835
Expenses:
Interest expense	4,924	6,617	12,458
Property operating expenses	257,510	383,907	374,370
Provision for depreciation	65,698	109,674	153,009
Total expenses	328,132	500,198	539,837
Income (loss) from real estate dispositions, net	$ 120,948	$ 165,186	$ 229,998