Financing Activities - Distributions (Details) - $ / shares	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Distributions (Numeric) [Abstract]
Dividend payable date of quarterly common stock dividend	Oct. 02, 2017
Current quarterly common stock dividend (in dollars per share)	$ 0.395	$ 0.3950	$ 0.38	$ 1.185	$ 1.14
Annualized current quarterly common stock dividend (in dollars per share)	$ 1.58