Net Assets - Additional Information (Details) - USD ($)				1 Months Ended	12 Months Ended				22 Months Ended	24 Months Ended
	Nov. 02, 2023	Oct. 25, 2021	Dec. 01, 2017	Oct. 31, 2015	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Mar. 24, 2021	Dec. 31, 2023	Sep. 29, 2021	Feb. 24, 2022	Mar. 31, 2020
Class Of Stock [Line Items]
Common stock, shares authorized					100,000,000	100,000,000			100,000,000
Common stock, par value					$ 0.01	$ 0.01			$ 0.01
Proceeds from common stock issued							$ 119,294,000
Issuance of common stock, value							119,294,000
Stock repurchased during period, shares					0	871,345			0
Stock repurchased during period, value						$ 10,800,000
Dividends common stock					$ 73,322,000	$ 51,593,000	$ 44,943,000
Stock issued during period, shares, dividend reinvestment plan					204,658	781,498	1,830,974
Stock issued during period, value, dividend reinvestment plan					$ 2,500,000	$ 10,900,000	$ 26,995,000
Maximum cost of shares that may be repurchased	$ 25,000,000				$ 25,000,000				$ 25,000,000		$ 25,000,000
Stock repurchase program, expiration date	Nov. 02, 2024				Feb. 24, 2023
Dividend Paid
Class Of Stock [Line Items]
Dividends common stock					$ 73,300,000
Dividends Paid In Cash
Class Of Stock [Line Items]
Dividends common stock					70,800,000	40,700,000	17,900,000
Dividend Declared
Class Of Stock [Line Items]
Dividends common stock					$ 73,300,000	$ 51,600,000	$ 44,900,000
R. David Spreng
Class Of Stock [Line Items]
Issuance of common stock, Shares				1,667
Issuance of common stock, value				$ 25,000
Runway Growth Holdings LLC
Class Of Stock [Line Items]
Issuance of common stock, Shares								22,564
Issuance of common stock, value								$ 300,000
Offering price								$ 15				$ 15
IPO
Class Of Stock [Line Items]
Issuance of common stock, Shares		6,850,000
Offering price		$ 14.6
Proceeds from common stock issued		$ 93,000,000
Initial Private Offering
Class Of Stock [Line Items]
Issuance of common stock, Shares			18,241,157
Issuance of common stock, value			$ 275,000,000
Second Private Offering
Class Of Stock [Line Items]
Issuance of common stock, Shares										9,617,379
Issuance of common stock, value										$ 144,300,000
Capital commitments										$ 181,700,000