Dividends and Distributions - Summary of Dividends Declarations and Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands														12 Months Ended
	Sep. 01, 2023	Aug. 18, 2023	Jun. 02, 2023	Mar. 03, 2023	Dec. 09, 2022	Sep. 02, 2022	Jun. 03, 2022	Mar. 04, 2022	Dec. 10, 2021	Sep. 08, 2021	Jun. 11, 2021	Mar. 05, 2021	Dec. 11, 2020	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Share-Based Payment Arrangement [Abstract]
Distribution to shareholders (in dollars per share)	$ 0.37	$ 0.04	$ 0.33	$ 0.33	$ 0.33	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.29	$ 0.29	$ 0.29	$ 0.29
Cash Distribution	$ 50,659	$ 5,495	$ 44,518	$ 43,548	$ 47,245	$ 40,223	$ 39,336	$ 37,358	$ 38,291	$ 35,852	$ 35,113	$ 34,311	$ 33,846	$ 238,392	$ 204,806	$ 194,852
DRIP shares issued (in shares)	0	0	0	0	0	0	0	29,928	837,158	876,727	920,150	972,196	0
DRIP Shares Value	$ 12,091	$ 1,289	$ 11,548	$ 12,848	$ 9,151	$ 11,046	$ 11,933	$ 13,902	$ 12,717	$ 13,203	$ 13,674	$ 14,194	$ 14,659
DRIP shares purchase (in shares)	824,353	90,264	854,808	959,844	689,422	903,318	917,845	882,358					1,034,149
DRIP shares purchase, weighted average exercised price per share (in dollars per share)	$ 14.67	$ 14.28	$ 13.51	$ 13.39	$ 13.27	$ 12.23	$ 13.00	$ 15.24					$ 14.18
Proceeds from stock issued during period, amount, DRIP								$ 457