Common and Preferred Shares Preferred Shares (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Preferred Stock [Line Items]
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 0	$ 0	$ 144,490
Series C Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Shares Issued	5,394,050	5,394,050
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	0.4049
Preferred shares conversion price	61.74
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 Stock, Dividends, Per Share, Cash Paid	1.4375	1.4375	$ 1.4375
Preferred Shares, Convertible, Conversion Adjustment	$ 0.6822	$ 0.6205
Series E Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Shares Issued	3,400,000	3,447,381
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	0.4759
Preferred shares conversion price	52.53
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 Stock, Dividends, Per Share, Cash Paid	2.25	2.25	$ 2.25
Preferred Shares, Convertible, Conversion Adjustment	$ 0.6024	$ 0.5308
Series G Preferred Stock [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Shares Issued	6,000,000	6,000,000
Preferred share dividend percentage	5.75%
Proceeds from Issuance of Preferred Stock and Preference Stock			$ 144,490
Preferred share dividend rate (in dollars per share)	$ 1.4375
Per share liquidation preference	25.00
Preferred Shares declared dividends per share		$ 1.4375
Preferred Stock, Dividends, Per Share, Cash Paid	1.4375	1.4375	$ 0.183681
Taxable Ordinary Income [Member] | Series C Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0.1050	0.5953
Preferred Stock, Dividends, Per Share, Cash Paid	1.2758	1.3791
Taxable Ordinary Income [Member] | Series E Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0	0.5092
Preferred Stock, Dividends, Per Share, Cash Paid	1.9970	2.1586
Taxable Ordinary Income [Member] | Series G Preferred Stock [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Cash Paid	1.2758	1.2105
Return of Capital [Member] | Series C Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0.5639	0
Preferred Stock, Dividends, Per Share, Cash Paid	0	0
Return of Capital [Member] | Series E Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0.6024	0
Preferred Stock, Dividends, Per Share, Cash Paid	0	0
Return of Capital [Member] | Series G Preferred Stock [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Cash Paid	0	0
Long-term Capital Gain [Member] | Series C Preferred Shares [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Non-cash Distributions	0.0133	0.0252
Unrecaptured Section 1250 gain	0.1617	0.0034
Dividends, Per Share, Non-cash Distributions, Unrecaptured Section 1250 Gain	0.0133	0.0015
Preferred Stock, Dividends, Per Share, Cash Paid	0.1617	0.0584
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	0.0216
Unrecaptured Section 1250 gain	0.2530	0.0053
Dividends, Per Share, Non-cash Distributions, Unrecaptured Section 1250 Gain	0	0.0013
Preferred Stock, Dividends, Per Share, Cash Paid	0.2530	0.0914
Long-term Capital Gain [Member] | Series G Preferred Stock [Member]
Schedule of Preferred Stock [Line Items]
Dividends, Per Share, Non-cash Distributions, Unrecaptured Section 1250 Gain	0.1617	0.0030
Preferred Stock, Dividends, Per Share, Cash Paid	0.1617	0.0513
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 G Preferred Stock [Member]
Schedule of Preferred Stock [Line Items]
Preferred Stock, Dividends, Per Share, Cash Paid	1.4375	1.2618
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	0.6822	0.6205
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	$ 0.6024	$ 0.5308