Shareholders' Equity Shareholders' Equity Summary of Dividends (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Common Shares [Member]
Dividends [Line Items]
Common Stock, Dividends, Per Share, Declared			$ 2.240	$ 2.110
Common Stock, Dividends, Per Share, Cash Paid			$ 2.190	$ 2.070
5.417% Series 1 Cumulative Convertible Preferred [Member]
Dividends [Line Items]
Preferred Stock, Dividend Rate, Percentage	5.417%	5.417%	5.417%	5.417%	5.417%
Preferred Stock, Dividends Per Share, Declared			$ 1.016	$ 1.016
Preferred Stock, Dividends, Per Share, Cash Paid			$ 1.016	$ 1.016