Consolidated Statements Of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues [Abstract]
Finance charges	$ 874.3	$ 730.5	$ 630.4
Premiums earned	43.0	48.2	52.3
Other Income	51.9	46.6	40.8
Total revenue	969.2	825.3	723.5
Costs and expenses [Abstract]
Salaries and wages	126.5	116.4	100.2
General and administrative	48.2	37.8	34.3
Sales and marketing	49.4	45.9	36.8
Provision for credit losses	90.2	41.5	12.8
Interest	97.7	76.0	56.7
Provision for claims	26.0	33.2	40.0
Loss on extinguishment of debt	0.0	0.0	21.8
Total costs and expenses	438.0	350.8	302.6
Income before provision for income taxes	531.2	474.5	420.9
Provision for income taxes	198.4	174.8	154.7
Net income	$ 332.8	$ 299.7	$ 266.2
Net income per share [Abstract]
Basic	$ 16.37	$ 14.35	$ 11.96
Diluted	$ 16.31	$ 14.28	$ 11.92
Weighted average Shares Outstanding [Abstract]
Basic	20,331,769	20,891,695	22,257,104
Diluted	20,410,116	20,980,753	22,331,401