Dividends (Details) - $ / shares		12 Months Ended
	Nov. 02, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Dividends [Abstract]
Series 1 Cumulative Convertible Preferred interest rate		5.417%	5.417%	5.417%
Common shares, declared	$ 0.98	$ 3.840	$ 3.620	$ 3.300
5.417% Series 1 Cumulative Convertible Preferred shares, declared		1.354	1.354	1.354
Common shares, paid		3.800	3.550	3.210
5.417% Series 1 Cumulative Convertible Preferred shares, paid		1.354	1.354	1.354
Common shares, ordinary dividend		3.800	3.515	3.178
Common shares, capital gain		0.000	0.035	0.032
5.417% Series 1 Cumulative Convertible Preferred shares, ordinary dividend		1.354	1.340	1.340
5.417% Series 1 Cumulative Convertible Preferred shares, capital gain		$ 0.000	$ 0.014	$ 0.014
Common Stock, Ordinary Dividends, Tax Rate		15.00%	15.00%	15.00%
Preferred Stock, Ordinary Dividends, Tax Rate		15.00%	15.00%	15.00%