Consolidated Statements Of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues [Abstract]
Finance Charges Revenue	$ 1,562.4	$ 1,369.4	$ 1,176.8
Premiums earned	57.3	51.0	46.6
Other Income	49.6	68.6	62.4
Total revenue	1,669.3	1,489.0	1,285.8
Costs and expenses [Abstract]
Salaries and wages	186.5	193.3	167.8
General and administrative	69.6	65.1	55.7
Sales and marketing	69.5	70.2	67.7
Provision for credit losses	556.9	76.4	56.9
Interest	192.0	196.2	156.6
Provision for claims	37.9	30.1	26.0
Loss on extinguishment of debt	7.4	1.8	0.0
Total costs and expenses	1,119.8	633.1	530.7
Income before provision for income taxes	549.5	855.9	755.1
Provision for income taxes	128.5	199.8	181.1
Net income	$ 421.0	$ 656.1	$ 574.0
Net income per share [Abstract]
Basic	$ 23.57	$ 34.71	$ 29.52
Diluted	$ 23.47	$ 34.57	$ 29.39
Weighted average Shares Outstanding [Abstract]
Basic	17,858,935	18,900,256	19,446,067
Diluted	17,935,779	18,976,560	19,532,312