Shareholders' Equity (Summary of Dividends) (Details) (USD $)	9 Months Ended	12 Months Ended	9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Common shares	Sep. 30, 2013 Common shares	Sep. 30, 2014 5.417% Series 1 Cumulative Convertible Preferred shares	Sep. 30, 2013 5.417% Series 1 Cumulative Convertible Preferred shares	Sep. 30, 2014 5.417% Series 1 Cumulative Convertible Preferred shares	Sep. 30, 2013 5.417% Series 1 Cumulative Convertible Preferred shares
Dividends [Line Items]
Preferred Shares, percentage	5.417%	5.417%			5.417%	5.417%	5.417%	5.417%
Dividends declared per common share			$ 2.43	$ 2.240
Dividends paid per common share			$ 2.34	$ 2.190
Dividends declared per preferred share							$ 1.016	$ 1.016
Dividends paid per preferred share							$ 1.016	$ 1.016