Equity Offerings, Offering Expenses, and Distributions - Common Stock Narrative (Details) - USD ($)						3 Months Ended		12 Months Ended
	Nov. 09, 2022	Jun. 09, 2022	Jul. 12, 2021	May 26, 2021	Aug. 03, 2020	Sep. 30, 2022	Sep. 30, 2021	Jun. 30, 2022	Dec. 01, 2022	Nov. 01, 2022	Oct. 31, 2022	Jun. 10, 2022	May 21, 2020	Aug. 24, 2011
Class of Stock [Line Items]
Stock repurchase program, authorized amount														$ 100,000,000
Stock repurchase program, remaining authorized repurchase amount						$ 65,860,000
Shares issued (in shares)							9,120,074
Market price threshold													95.00%
Outstanding shares threshold												25.00%
Payments of dividends, common stock						$ 71,072,000	$ 70,043,000
Shares issued through reinvestment of dividends (in shares)							1,955
Shares issued through reinvestment of dividends rate						0.002%
Convertible Notes
Class of Stock [Line Items]
Capital shares reserved for future issuance (in shares)						17,294,357
Officers and Directors
Class of Stock [Line Items]
Shares issued through reinvestment of dividends (in shares)						6,650
5.50% Preferred Stock
Class of Stock [Line Items]
Dividend rate		5.50%				5.50%		5.50%
Dividend rate			5.50%	5.50%	5.50%	5.50%	5.50%
Capital shares reserved for future issuance (in shares)						1,000,000,000
5.50% Preferred Stock | Subsequent Event
Class of Stock [Line Items]
Dividend rate	5.50%
5.50% Preferred Stock | Dividend Declared | Subsequent Event
Class of Stock [Line Items]
Dividends payable (usd per share)									$ 0.114583	$ 0.114583
Common Stock
Class of Stock [Line Items]
Stock repurchased during period (in shares)						0	0
Shares issued (in shares)						0	0
Shares issued through reinvestment of dividends (in shares)						2,154,958	1,079,168
Common Stock | Dividend Declared | Subsequent Event
Class of Stock [Line Items]
Dividends payable (usd per share)											$ 0.06