Common and Preferred Shares Preferred Shares (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Series C Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Shares Issued	5,399,050	5,400,000
Preferred share dividend percentage	5.75%
Preferred share dividend rate (in dollars per share)	$ 1.4375
Per share liquidation preference	25
Preferred shares conversion rate	0.3785
Preferred shares conversion price	66.05
Common shares quarterly dividend per share threshold, minimum	$ 0.6875
Common share closing price percent of preferred share prevailing conversion price, minimum	135.00%
Preferred Shares declared dividends per share	$ 1.4375	$ 1.4375
Preferred Shares, Convertible, Conversion Adjustment	$ 0.4394
Series E Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Shares Issued	3,450,000	3,450,000
Preferred share dividend percentage	9.00%
Preferred share dividend rate (in dollars per share)	$ 2.25
Per share liquidation preference	25
Preferred shares conversion rate	0.4569
Preferred shares conversion price	54.72
Common shares quarterly dividend per share threshold, minimum	$ 0.84
Common share closing price percent of preferred share prevailing conversion price, minimum	150.00%
Preferred Shares declared dividends per share	$ 2.25	$ 2.25
Preferred Shares, Convertible, Conversion Adjustment	$ 0.2139
Series F Preferred Stock [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Shares Issued	5,000,000	5,000,000
Preferred share dividend percentage	6.625%
Preferred share dividend rate (in dollars per share)	$ 1.65625
Per share liquidation preference	25.00
Preferred Shares declared dividends per share	1.65625	$ 1.65625
Taxable Ordinary Income [Member] | Series C Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0.2850	0.0000
Preferred Stock, Dividends, Per Share, Cash Paid	1.2735	1.4375
Taxable Ordinary Income [Member] | Series E Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0.0883	0.0000
Preferred Stock, Dividends, Per Share, Cash Paid	1.9933	2.2500
Taxable Ordinary Income [Member] | Series F Preferred Stock [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Cash Paid	1.4673	1.6563
Return of Capital [Member] | Series C Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0.1177	0.0000
Preferred Stock, Dividends, Per Share, Cash Paid	0.0000	0.0000
Return of Capital [Member] | Series E Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0.1142	0.0000
Preferred Stock, Dividends, Per Share, Cash Paid	0.0000	0.0000
Return of Capital [Member] | Series F Preferred Stock [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Cash Paid	0.0000	0.0000
Long-term Capital Gain [Member] | Series C Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0.0367	0.0000
Unrecaptured Section 1250 gain	0.0426
Dividends, Per Share, Non-cash Distributions, Unrecaptured Section 1250 Gain	0.0095
Preferred Stock, Dividends, Per Share, Cash Paid	0.1640	0.0000
Long-term Capital Gain [Member] | Series E Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0.0114	0.0000
Unrecaptured Section 1250 gain	0.0668
Dividends, Per Share, Non-cash Distributions, Unrecaptured Section 1250 Gain	0.0030
Preferred Stock, Dividends, Per Share, Cash Paid	0.2567	0.0000
Long-term Capital Gain [Member] | Series F Preferred Stock [Member]
Schedule of Preferred Stock [Line Items]
Unrecaptured Section 1250 gain	0.0491
Preferred Stock, Dividends, Per Share, Cash Paid	0.1889	0.0000
Total Cash Distribution Per Share [Member] | Series C Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Cash Paid	1.4375	1.4375
Total Cash Distribution Per Share [Member] | Series E Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Cash Paid	2.2500	2.2500
Total Cash Distribution Per Share [Member] | Series F Preferred Stock [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Cash Paid	1.6562	1.6563
Total non-cash Distributions Per Share [Domain] | Series C Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0.4394	0.0000
Total non-cash Distributions Per Share [Domain] | Series E Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	$ 0.2139	$ 0.0000