v3.26.1
Consolidated Statements of Changes in Net Assets - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Increase (decrease) in net assets resulting from operations:        
Net investment income $ 24,622 $ 34,585 $ 55,253 $ 69,226
Net realized (losses) gains on investments and foreign currency (44,984) 13,389 (76,994) 51,214
Net change in unrealized appreciation (depreciation) of investments, foreign currency and New Mountain Net Lease Corporation 37,816 (40,078) (3,841) (89,005)
Net change in unrealized depreciation of securities purchased under collateralized agreements to resell 0 0 (7,800) 0
Benefit (provision) for taxes 59 (21) 146 (43)
Net increase (decrease) in net assets resulting from operations 17,513 7,875 (33,236) 31,392
Capital transactions        
Repurchase of shares under the repurchase programs (8,966) (9,642) (65,563) (9,642)
Distributions declared to stockholders from net investment income (23,702) (34,589)    
New Mountain Finance Corporation net assets at the beginning of the period 1,049,970 1,348,178 1,188,256 1,359,291
Net assets at the end of the period $ 1,034,815 $ 1,311,836 $ 1,034,815 $ 1,311,836
Capital share activity        
Conversion of 2022 Convertible Notes to Shares (in shares) 0 514 0 514
Shares repurchased under the repurchase programs (in shares) (1,122,761) (925,216) (8,185,998) (925,216)
Net decrease in shares outstanding (in shares) (1,122,761) (924,702) (8,185,998) (924,702)
Non-Controlling Interest in NMNLC        
Increase (decrease) in net assets resulting from operations:        
Net increase (decrease) in net assets resulting from operations $ 256 $ 101 $ 435 $ 205
Capital transactions        
Distributions declared to stockholders from net investment income (90) (90)    
New Mountain Finance Corporation net assets at the beginning of the period 6,468 5,966 6,079 5,952
Net assets at the end of the period 6,634 5,977 6,634 5,977
New Mountain Finance Corporation        
Increase (decrease) in net assets resulting from operations:        
Net increase (decrease) in net assets resulting from operations 17,257 7,774 (33,671) 31,187
Capital transactions        
Repurchase of shares under the repurchase programs (8,966) (9,642) (65,563) (9,642)
Offering costs 0 14 0 (14)
Distributions declared to stockholders from net investment income (23,612) (34,499) (54,762) (69,011)
Total net decrease in net assets resulting from capital transactions (32,578) (44,127) (120,325) (78,667)
Net decrease in net assets (15,321) (36,353) (153,996) (47,480)
New Mountain Finance Corporation net assets at the beginning of the period 1,043,502 1,342,212 1,182,177 1,353,339
Net assets at the end of the period $ 1,028,181 $ 1,305,859 $ 1,028,181 $ 1,305,859