Equity and Capital Equity and Capital Tax Status of Dividends (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Tax Status of Dividends [Abstract]
Common stock/unit per share	$ 2.00	$ 1.94	$ 1.88
Allocation of Dividends, Ordinary Income	53.00%	71.00%	70.00%
Allocation of Dividends, Capital Gain	8.00%	5.00%	16.00%
Allocation of Dividends, Return of Capital	39.00%	19.00%	14.00%
Allocation of Dividends, Qualified Dividend Income	0.00%	5.00%	0.00%