Income Taxes Income Taxes (Schedule of Dividends Paid, Per Share) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock, Dividends, Per Share, Cash Paid	$ 4.00	$ 3.80	$ 3.60
Ordinary Income [Member]
Common Stock, Dividends, Per Share, Cash Paid	3.3373	2.93054	2.678634
Capital Gain [Member]
Common Stock, Dividends, Per Share, Cash Paid	0	0.20643	0.921366
Return of Capital [Member]
Common Stock, Dividends, Per Share, Cash Paid	$ 0.6627	$ 0.66303	$ 0