v3.26.1
SHORT TERM AND LONG-TERM DEBT - Short Term and Long-Term Debt Components (Details) - USD ($)
Jun. 30, 2026
Dec. 31, 2025
Debt Instrument [Line Items]    
Total debt $ 1,805,103,000 $ 1,860,608,000
Current portion of debt (112,688,000) (111,614,000)
Long-term portion of debt issuance costs (9,567,000) (10,416,000)
Long-term debt 1,682,848,000 1,738,578,000
Floating rate long-term debt    
Debt Instrument [Line Items]    
Total debt 1,264,118,000 1,315,790,000
Floating rate long-term debt | $66 million term tranche under the Flex Enterprise $150 Million Facility    
Debt Instrument [Line Items]    
Face amount 66,000,000  
Floating rate long-term debt | $140 million term tranche under the $290 Million Facility    
Debt Instrument [Line Items]    
Face amount 140,000,000  
Total debt 92,792,000 100,054,000
Floating rate long-term debt | $90 million term tranche under the $270 Million Facility    
Debt Instrument [Line Items]    
Face amount 90,000,000  
Total debt 65,486,000 73,658,000
Floating rate long-term debt | Flex Constellation $180 Million Facility    
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity 180,000,000  
Total debt 172,500,000 177,500,000
Floating rate long-term debt | $330 Million Sale and Leaseback    
Debt Instrument [Line Items]    
Gross price 330,000,000  
Total debt 270,500,000 279,000,000
Floating rate long-term debt | Flex Rainbow $180 Million Sale and Leaseback    
Debt Instrument [Line Items]    
Gross price 180,000,000  
Total debt 151,182,000 155,966,000
Floating rate long-term debt | Flex Endeavour $160 Million Sale and Leaseback    
Debt Instrument [Line Items]    
Gross price 160,000,000  
Total debt 146,182,000 150,292,000
Floating rate long-term debt | Flex Courageous $175 Million Sale and Leaseback    
Debt Instrument [Line Items]    
Gross price 175,000,000  
Total debt 166,875,000 171,325,000
Floating rate long-term debt | Flex Resolute $175 Million Sale and Leaseback    
Debt Instrument [Line Items]    
Gross price 175,000,000  
Total debt 169,123,000 173,604,000
Line of credit    
Debt Instrument [Line Items]    
Total debt 413,675,000 413,675,000
Line of credit | $66 million term tranche under the Flex Enterprise $150 Million Facility    
Debt Instrument [Line Items]    
Total debt 29,478,000 34,391,000
Line of credit | Flex Enterprise $150 million facility    
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity 150,000,000  
Line of credit | $290 million facility    
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity 290,000,000  
Line of credit | $270 million facility    
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity 270,000,000  
Line of credit | $84 million revolving tranche under the Flex Enterprise $150 Million Facility    
Debt Instrument [Line Items]    
Face amount 84,000,000  
Total debt 83,675,000 83,675,000
Line of credit | $150 million revolving tranche under the $290 Million Facility    
Debt Instrument [Line Items]    
Face amount 150,000,000  
Total debt 150,000,000 150,000,000
Line of credit | $180 million revolving tranche under the $270 Million Facility    
Debt Instrument [Line Items]    
Face amount 180,000,000  
Total debt 180,000,000 180,000,000
Fixed rate long-term debt    
Debt Instrument [Line Items]    
Total debt 127,310,000 131,143,000
Fixed rate long-term debt | Flex Volunteer Sale and Leaseback    
Debt Instrument [Line Items]    
Total debt $ 127,310,000 $ 131,143,000