v3.26.3
Consolidated Statements of Changes in Net Assets - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Increase (decrease) in net assets resulting from operations:        
Net investment income $ 23,693 $ 34,042 $ 78,946 $ 103,268
Net realized (losses) gains on investments and foreign currency (532) 9 (77,526) 51,223
Net change in unrealized (depreciation) appreciation of investments, foreign currency and New Mountain Net Lease Corporation (19,250) (21,684) (23,091) (110,689)
Net change in unrealized depreciation of securities purchased under collateralized agreements to resell 0 0 (7,800) 0
Provision for taxes (168) (25) (22) (68)
Net increase (decrease) in net assets resulting from operations 3,743 12,342 (29,493) 43,734
Capital transactions        
Repurchase of shares under the repurchase programs   (27,611) (65,563) (37,253)
Conversion of 2022 Convertible Notes to Shares   7    
Distributions declared to stockholders from net investment income (24,350) (33,912)    
New Mountain Finance Corporation net assets at the beginning of the period 1,034,815 1,311,836 1,188,256 1,359,291
New Mountain Finance Corporation net assets at the end of the period $ 1,014,208 $ 1,262,666 $ 1,014,208 $ 1,262,666
Capital share activity        
Conversion of 2022 Convertible Notes to Shares (in shares) 0 0 0 514
Shares repurchased under the repurchase programs (in shares) 0 (2,737,377) (8,185,998) (3,662,593)
Net decrease in shares outstanding (in shares) 0 (2,737,377) (8,185,998) (3,662,079)
Non-Controlling Interest in NMNLC        
Increase (decrease) in net assets resulting from operations:        
Net increase (decrease) in net assets resulting from operations $ 264 $ 153 $ 699 $ 358
Capital transactions        
Distributions declared to stockholders from net investment income (737) (90)    
New Mountain Finance Corporation net assets at the beginning of the period 6,634 5,977 6,079 5,952
New Mountain Finance Corporation net assets at the end of the period 6,161 6,040 6,161 6,040
New Mountain Finance Corporation        
Increase (decrease) in net assets resulting from operations:        
Net increase (decrease) in net assets resulting from operations 3,479 12,189 (30,192) 43,376
Capital transactions        
Repurchase of shares under the repurchase programs 0 (27,611) (65,563) (37,253)
Conversion of 2022 Convertible Notes to Shares 0 7 0 7
Offering costs 0 4 0 (10)
Distributions declared to stockholders from net investment income (23,613) (33,822) (78,375) (102,833)
Total net decrease in net assets resulting from capital transactions (23,613) (61,422) (143,938) (140,089)
Net decrease in net assets (20,134) (49,233) (174,130) (96,713)
New Mountain Finance Corporation net assets at the beginning of the period 1,028,181 1,305,859 1,182,177 1,353,339
New Mountain Finance Corporation net assets at the end of the period $ 1,008,047 $ 1,256,626 $ 1,008,047 $ 1,256,626