Shareholders' Equity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Share Dividend Declared
Dividend per common share	$ 1.60	$ 1.50	$ 1.20
Preferred Share Dividend Declared
Dividend per preferred share	1.9375	1.9375	1.9375
First Quarter [Member]
Common Share Dividend Declared
Dividend per common share	0.40	0.35	0.30
Preferred Share Dividend Declared
Dividend per preferred share	0.484375	0.484375	0.484375
Second Quarter [Member]
Common Share Dividend Declared
Dividend per common share	0.40	0.35	0.30
Preferred Share Dividend Declared
Dividend per preferred share	0.484375	0.484375	0.484375
Third Quarter [Member]
Common Share Dividend Declared
Dividend per common share	0.40	0.40	0.30
Preferred Share Dividend Declared
Dividend per preferred share	0.484375	0.484375	0.484375
Fourth Quarter [Member]
Common Share Dividend Declared
Dividend per common share	0.40	0.40	0.30
Preferred Share Dividend Declared
Dividend per preferred share	$ 0.484375	$ 0.484375	$ 0.484375