Income Taxes Income Taxes (Schedule of Dividends Paid, Per Share) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock, Dividends, Per Share, Cash Paid	$ 3.60	$ 3.40	$ 3.08
Ordinary Income [Member]
Common Stock, Dividends, Per Share, Cash Paid	2.678634	2.62808	2.535481
Capital Gain [Member]
Common Stock, Dividends, Per Share, Cash Paid	0.921366	0.69110	0
Return of Capital [Member]
Common Stock, Dividends, Per Share, Cash Paid	$ 0	$ 0.08082	$ 0.544519