Income Taxes Charaterization of Distributions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Dividends per common share:	$ 2.60	$ 2.60	$ 2.60
Percent of Total Dividends Paid	100.00%	100.00%	100.00%
Ordinary Income [Member]
Income Tax Contingency [Line Items]
Dividends per common share:	$ 0.81	$ 1.08	$ 0.82
Percent of Total Dividends Paid	31.20%	41.70%	31.70%
Capital Gains [Member]
Income Tax Contingency [Line Items]
Dividends per common share:	$ 0.51	$ 0.78	$ 0.64
Percent of Total Dividends Paid	19.60%	30.10%	24.60%
Return of Capital [Member]
Income Tax Contingency [Line Items]
Dividends per common share:	$ 1.28	$ 0.74	$ 1.14
Percent of Total Dividends Paid	49.20%	28.20%	43.70%