v3.26.1
Financial Data of Business Segments (Details)
 3 Months Ended 6 Months Ended
Jun. 30, 2026
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
Segment
Jun. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Segment Reporting [Abstract]          
Number of business segments | Segment     3    
Number of Reportable Segments | Segment     3    
Payment for management fee $ 1,500,000 $ 1,300,000 $ 3,000,000.0 $ 2,700,000  
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Lease revenue 508,400,000 368,800,000 1,027,100,000 728,400,000  
Non-dedicated engine revenue 20,600,000 20,500,000 42,700,000 42,000,000.0  
Other revenue 51,100,000 41,200,000 94,000,000.0 81,700,000  
Total Revenues 580,100,000 430,500,000 1,163,800,000 852,100,000  
Maintenance expense 151,800,000 104,500,000 292,500,000 208,000,000.0  
Depreciation expense 166,500,000 106,900,000 335,700,000 210,500,000  
Operating lease expense 7,400,000 7,100,000 14,800,000 14,700,000  
Other operating expense 24,800,000 16,500,000 46,600,000 32,500,000  
Total Expenses 350,500,000 235,000,000.0 689,600,000 465,700,000  
Net gain on asset dispositions 69,700,000 40,500,000 120,700,000 73,900,000  
Interest expense, net (143,000,000.0) (96,200,000) (294,000,000.0) (191,100,000)  
Other (expense) income 12,700,000 (1,100,000) 18,900,000 (3,800,000)  
Share of affiliates' earnings (pre-tax) 49,600,000 22,500,000 77,200,000 55,900,000  
Segment profit (loss) 218,600,000 161,200,000 397,000,000.0 321,300,000  
Selling, general and administrative expense 69,200,000 58,200,000 140,500,000 114,800,000  
Net Income Attributable to GATX 103,400,000 75,500,000 188,900,000 154,100,000  
Net gains on disposition of owned assets 59,100,000 34,100,000 103,200,000 65,200,000  
Residual sharing income 100,000 200,000 200,000 300,000  
Non-remarketing net gains 10,500,000 6,200,000 19,000,000.0 12,000,000.0  
Asset impairments     1,700,000 3,600,000  
Net gain on asset dispositions 69,700,000 40,500,000 120,700,000 73,900,000  
Cash paid for the acquisition of operating assets 200,500,000 219,000,000.0 4,720,500,000 515,300,000  
Investments in affiliated companies 721,900,000   721,900,000   $ 732,300,000
Identifiable assets 17,720,900,000   17,720,900,000   17,999,500,000
Income taxes, affiliates' earnings 12,400,000 6,500,000 (19,200,000) 14,800,000  
Total expenses (1) 419,700,000 293,200,000 830,100,000 580,500,000  
Income taxes expense (benefit) including affiliate's earnings 38,400,000 27,500,000 66,400,000 52,400,000  
Net Income 111,000,000.0 75,500,000 190,100,000 154,100,000  
Net income 7,600,000 0 1,200,000 0  
Payment for management fee 1,500,000 1,300,000 3,000,000.0 2,700,000  
Proceeds from dividends received 70,000,000.0 0 70,000,000.0 0  
Brookfield          
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Other revenue 2,800,000   5,600,000    
GABX          
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Depreciation expense  
Rail North America          
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Lease revenue 391,000,000.0 262,800,000 791,700,000 522,800,000  
Other revenue 44,000,000.0 32,900,000 80,000,000.0 66,200,000  
Total Revenues 435,000,000.0 295,700,000 871,700,000 589,000,000.0  
Maintenance expense 131,800,000 84,300,000 252,400,000 168,000,000.0  
Depreciation expense 124,000,000.0 71,700,000 250,700,000 142,100,000  
Operating lease expense 7,400,000 7,100,000 14,800,000 14,700,000  
Other operating expense 15,800,000 7,800,000 28,900,000 15,300,000  
Total Expenses 279,000,000.0 170,900,000 546,800,000 340,100,000  
Net gain on asset dispositions 67,700,000 39,100,000 117,500,000 71,200,000  
Interest expense, net (103,700,000) (64,400,000) (217,700,000) (129,100,000)  
Other (expense) income (1,500,000) (2,800,000) (2,300,000) (5,500,000)  
Share of affiliates' earnings (pre-tax) 0 (100,000) 0 (100,000)  
Segment profit (loss) 118,500,000 96,600,000 222,400,000 185,400,000  
Net gains on disposition of owned assets 58,300,000 34,100,000 102,300,000 64,600,000  
Residual sharing income 100,000 200,000 200,000 300,000  
Non-remarketing net gains 9,300,000 4,800,000 16,700,000 9,900,000  
Asset impairments     1,700,000 3,600,000  
Net gain on asset dispositions 67,700,000 39,100,000 117,500,000 71,200,000  
Cash paid for the acquisition of operating assets 147,100,000 132,200,000 4,611,300,000 359,900,000  
Identifiable assets 12,193,100,000   12,193,100,000   12,235,500,000
Rail North America | RailPulse          
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Investments in affiliated companies 200,000   200,000   0
Rail International          
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Lease revenue 100,300,000 89,600,000 200,700,000 173,200,000  
Other revenue 5,300,000 6,200,000 10,100,000 11,100,000  
Total Revenues 105,600,000 95,800,000 210,800,000 184,300,000  
Maintenance expense 19,200,000 18,900,000 38,300,000 37,400,000  
Depreciation expense 27,900,000 21,700,000 55,700,000 41,800,000  
Operating lease expense 0 0 0 0  
Other operating expense 4,900,000 4,900,000 10,200,000 9,500,000  
Total Expenses 52,000,000.0 45,500,000 104,200,000 88,700,000  
Net gain on asset dispositions 2,000,000.0 1,400,000 3,100,000 2,700,000  
Interest expense, net (23,900,000) (20,000,000.0) (48,900,000) (39,100,000)  
Other (expense) income (100,000) 500,000 2,400,000 (1,300,000)  
Share of affiliates' earnings (pre-tax) 0 0 0 0  
Segment profit (loss) 31,600,000 32,200,000 63,200,000 57,900,000  
Net gains on disposition of owned assets 800,000 0 800,000 600,000  
Residual sharing income 0 0 0 0  
Non-remarketing net gains 1,200,000 1,400,000 2,300,000 2,100,000  
Asset impairments     0 0  
Net gain on asset dispositions 2,000,000.0 1,400,000 3,100,000 2,700,000  
Cash paid for the acquisition of operating assets 45,600,000 81,100,000 93,000,000.0 143,800,000  
Investments in affiliated companies         0
Identifiable assets 2,821,100,000   2,821,100,000   2,919,000,000
Rail International | RailPulse          
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Investments in affiliated companies 0   0    
Engine Leasing          
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Lease revenue 8,800,000 8,100,000 18,300,000 16,200,000  
Non-dedicated engine revenue 20,600,000 20,500,000 42,700,000 42,000,000.0  
Other revenue 0 0 0 0  
Total Revenues 29,400,000 28,600,000 61,000,000.0 58,200,000  
Other operating expense 3,000,000.0 2,900,000 6,100,000 5,700,000  
Net gain on asset dispositions 0 0 0 0  
Net gains on disposition of owned assets 0 0 0 0  
Residual sharing income 0 0 0 0  
Non-remarketing net gains 0 0 0 0  
Asset impairments     0 0  
Net gain on asset dispositions 0 0 0 0  
Cash paid for the acquisition of operating assets 0 0 200,000 0  
Investments in affiliated companies         732,300,000
Identifiable assets 1,871,100,000   1,871,100,000   1,831,600,000
Engine Leasing | RailPulse          
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Investments in affiliated companies 721,700,000   721,700,000    
Other          
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Lease revenue 8,300,000 8,300,000 16,400,000 16,200,000  
Other revenue 1,800,000 2,100,000 3,900,000 4,400,000  
Total Revenues 10,100,000 10,400,000 20,300,000 20,600,000  
Maintenance expense 800,000 1,300,000 1,800,000 2,600,000  
Depreciation expense 4,000,000.0 4,000,000.0 8,100,000 7,700,000  
Operating lease expense 0 0 0 0  
Other operating expense 1,100,000 900,000 1,400,000 2,000,000.0  
Total Expenses 5,900,000 6,200,000 11,300,000 12,300,000  
Net gain on asset dispositions 0 0 100,000 0  
Interest expense, net (2,700,000) (200,000) (1,400,000) 900,000  
Other (expense) income 600,000 1,100,000 2,000,000.0 2,900,000  
Share of affiliates' earnings (pre-tax) 0 0 0 0  
Segment profit (loss) 2,100,000 5,100,000 9,700,000 12,100,000  
Net gains on disposition of owned assets 0 0 100,000 0  
Residual sharing income 0 0 0 0  
Non-remarketing net gains 0 0 0 0  
Asset impairments     0 0  
Net gain on asset dispositions 0 0 100,000 0  
Cash paid for the acquisition of operating assets 7,800,000 5,700,000 16,000,000.0 11,600,000  
Investments in affiliated companies         0
Identifiable assets 835,600,000   835,600,000   $ 1,013,400,000
Other | RailPulse          
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Investments in affiliated companies 0   0    
Portfolio Management          
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]          
Maintenance expense 0 0 0 0  
Depreciation expense 10,600,000 9,500,000 21,200,000 18,900,000  
Operating lease expense 0 0 0 0  
Total Expenses 13,600,000 12,400,000 27,300,000 24,600,000  
Net gain on asset dispositions 0 0 0 0  
Interest expense, net (12,700,000) (11,600,000) (26,000,000.0) (23,800,000)  
Other (expense) income 13,700,000 100,000 16,800,000 100,000  
Share of affiliates' earnings (pre-tax) 49,600,000 22,600,000 77,200,000 56,000,000.0  
Segment profit (loss) 66,400,000 27,300,000 101,700,000 65,900,000  
Net gain on asset dispositions $ 0 $ 0 $ 0 $ 0