Variable interest entities and asset securitizations - Asset-backed Notes Issued to Investors (Details) - USD ($)	3 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Variable Interest Entity [Line Items]
Asset-Backed Notes to Investors	$ 2,027,000,000	$ 1,730,000,000
August 2023 \| Equipment finance loans and leases
Variable Interest Entity [Line Items]
Remaining Loan Collateral Balance	209,000,000	244,000,000
Asset-Backed Notes to Investors	$ 109,000,000	141,000,000
Weighted-Average Life (In years)	6 months
Weighted-Average Rate	5.74%
March 2024 \| Automobile loans
Variable Interest Entity [Line Items]
Remaining Loan Collateral Balance	$ 223,000,000	252,000,000
Asset-Backed Notes to Investors	$ 211,000,000	239,000,000
Weighted-Average Life (In years)	1 year 1 month 6 days
Weighted-Average Rate	5.20%
August 2024 \| Equipment finance loans and leases
Variable Interest Entity [Line Items]
Remaining Loan Collateral Balance	$ 432,000,000	483,000,000
Asset-Backed Notes to Investors	$ 355,000,000	396,000,000
Weighted-Average Life (In years)	1 year 3 months 18 days
Weighted-Average Rate	4.84%
February 2025 \| Automobile loans
Variable Interest Entity [Line Items]
Remaining Loan Collateral Balance	$ 476,000,000	529,000,000
Asset-Backed Notes to Investors	$ 460,000,000	513,000,000
Weighted-Average Life (In years)	1 year 3 months 18 days
Weighted-Average Rate	4.68%
May 2025 \| Equipment finance loans and leases
Variable Interest Entity [Line Items]
Remaining Loan Collateral Balance	$ 501,000,000	546,000,000
Asset-Backed Notes to Investors	$ 406,000,000	441,000,000
Weighted-Average Life (In years)	1 year 7 months 6 days
Weighted-Average Rate	4.76%
February 2026 \| Recreational finance loans
Variable Interest Entity [Line Items]
Remaining Loan Collateral Balance	$ 544,000,000	0
Asset-Backed Notes to Investors	$ 486,000,000	$ 0
Weighted-Average Life (In years)	4 years 7 months 6 days
Weighted-Average Rate	4.35%