STATEMENTS OF COMPREHENSIVE INCOME AND RETAINED EARNINGS - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023		Sep. 30, 2022
Income Statement [Abstract]
Interest and fee income	$ 125.5	$ 80.9	$ 338.2		$ 225.5
Operating lease and rental revenues	54.9	75.7	186.8		232.6
Used truck sales and other revenues	3.8	3.8	15.5		15.2
TOTAL INTEREST AND OTHER REVENUES	184.2	160.4	540.5		473.3
Interest and other borrowing costs	74.9	35.2	192.1		92.5
Depreciation and other rental expenses	47.1	51.3	138.8		137.5
Cost of used truck sales and other expenses	2.6	1.7	11.2		7.7
Selling, general and administrative expenses	16.3	15.5	47.9		45.6
Provision for losses on receivables	0.8	(1.2)	2.2		(3.6)
TOTAL EXPENSES	141.7	102.5	392.2		279.7
INCOME BEFORE INCOME TAXES	42.5	57.9	148.3		193.6
Income taxes	10.3	14.4	36.7		47.7
NET INCOME	32.2	43.5	111.6		145.9
COMPREHENSIVE INCOME	34.3	44.7	112.2		168.8
RETAINED EARNINGS AT BEGINNING OF PERIOD	1,643.0	1,719.2	1,813.6	[1]	1,716.8
RETAINED EARNINGS AT END OF PERIOD	$ 1,675.2	$ 1,762.7	$ 1,675.2		$ 1,762.7

[1] The December 31, 2022 balance sheet has been derived from audited financial statements.