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Subsequent Events - Monthly Distributions Declared by Company's Board of Directors (Detail) - $ / shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 Months Ended |
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Jul. 06, 2020 | Jul. 02, 2020 | Jun. 30, 2020 | Jun. 25, 2020 | Jun. 19, 2020 | Jun. 05, 2020 | May 29, 2020 | May 28, 2020 | May 19, 2020 | May 06, 2020 | May 05, 2020 | Apr. 30, 2020 | Apr. 29, 2020 | Apr. 24, 2020 | Jun. 30, 2020 | May 31, 2020 | Apr. 30, 2020 | Apr. 14, 2020
Subsequent event | Series D Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.4374999
Subsequent event | Series E Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.414063
Subsequent event | Series F Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.375
Subsequent event | Senior Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.2625
Subsequent event | Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.37545
Subsequent event | April 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Record Date |  |  |  |  |  |  |  |  |  |  |  |  |  | Apr. 24, 2020 |  |  |  |
Forecast | May 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Record Date |  |  |  |  |  |  |  |  | May 19, 2020 |  |  |  |  |  |  |  |  |
Payment Date |  |  |  |  |  |  | May 29, 2020 |  |  |  |  |  |  |  |  |  |  |
Forecast | May 2020 | Series D Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  | $ 0.1458333 |  |  |  |  |  |  |  |  |  |  |
Forecast | May 2020 | Series E Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  | 0.138021 |  |  |  |  |  |  |  |  |  |  |
Forecast | May 2020 | Series F Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payable to the Holders of Record During the Month of: |  |  |  |  |  |  |  | May 28, 2020 |  |  |  |  |  |  |  |  |  |
Payment Date |  |  |  |  |  | Jun. 05, 2020 |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  | $ 0.125 |  |  |  |  |  |  |  |  |  |  |  |
Forecast | May 2020 | Senior Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payable to the Holders of Record During the Month of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | May |  |
Payment Date |  |  |  |  |  | Jun. 05, 2020 |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  | $ 0.0875 |  |  |  |  |  |  |  |  |  |  |  |
Forecast | May 2020 | Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  | $ 0.12515 |  |  |  |  |  |  |  |  |  |  |
Forecast | June 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Record Date |  |  |  |  | Jun. 19, 2020 |  |  |  |  |  |  |  |  |  |  |  |  |
Payment Date |  |  | Jun. 30, 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Forecast | June 2020 | Series D Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  | $ 0.1458333 |  |  |  |  |  |  |  |  |  |  |  | $ 0.1458333 |  |  |
Forecast | June 2020 | Series E Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  | 0.138021 |  |  |  |  |  |  |  |  |  |  |  | $ 0.138021 |  |  |
Forecast | June 2020 | Series F Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payable to the Holders of Record During the Month of: |  |  |  | June 25, 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payment Date |  | Jul. 02, 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  | $ 0.125 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Forecast | June 2020 | Senior Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payable to the Holders of Record During the Month of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  | June |  |  |
Payment Date | Jul. 06, 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) | $ 0.0875 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Forecast | June 2020 | Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  | $ 0.12515 |  |  |  |  |  |  |  |  |  |  |  | $ 0.12515 |  |  |
Forecast | Subsequent event | April 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payment Date |  |  |  |  |  |  |  |  |  |  |  | Apr. 30, 2020 |  |  |  |  |  |
Forecast | Subsequent event | April 2020 | Series D Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  |  |  |  |  |  | $ 0.1458333 |  |  |  |  | $ 0.1458333 |
Forecast | Subsequent event | April 2020 | Series E Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  |  |  |  |  |  | 0.138021 |  |  |  |  | $ 0.138021 |
Forecast | Subsequent event | April 2020 | Series F Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payable to the Holders of Record During the Month of: |  |  |  |  |  |  |  |  |  |  |  |  | April 29, 2020 |  |  |  |  |
Payment Date |  |  |  |  |  |  |  |  |  |  | May 05, 2020 |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  |  |  |  |  | $ 0.125 |  |  |  |  |  |  |
Forecast | Subsequent event | April 2020 | Senior Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payable to the Holders of Record During the Month of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | April |
Payment Date |  |  |  |  |  |  |  |  |  | May 06, 2020 |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  |  |  |  | $ 0.0875 |  |  |  |  |  |  |  |
Forecast | Subsequent event | April 2020 | Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution per share (in dollars per share) |  |  |  |  |  |  |  |  |  |  |  | $ 0.12515 |  |  |  |  | $ 0.12515 |

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