Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash Flows From Operating Activities:
Net income	$ 293.1	$ 245.2
Adjustments to reconcile cash provided by operating activities:
Provision for credit losses	68.0	62.8
Depreciation	4.7	4.7
Amortization	7.5	6.8
Loss on retirement of property and equipment	0.1	0.1
Provision for deferred income taxes	60.5	32.0
Stock-based compensation	8.3	5.6
Change in operating assets and liabilities:
Increase in accounts payable and accrued liabilities	(2.8)	(0.9)
Decrease (increase) in income taxes receivable	(3.2)	4.6
Increase (decrease) in income taxes payable	(23.4)	2.0
Decrease in other assets	1.8	0.6
Net cash provided by operating activities	414.6	363.5
Cash Flows From Investing Activities:
Increase in restricted cash and cash equivalents	(48.9)	(65.4)
Purchases of restricted securities available for sale	(28.0)	(28.3)
Proceeds from sale of restricted securities available for sale	23.0	25.5
Maturities of restricted securities available for sale	4.3	4.5
Principal collected on Loans receivable	1,657.4	1,493.2
Advances to Dealers	(1,467.2)	(1,476.4)
Purchases of Consumer Loans	(686.7)	(589.4)
Accelerated payments of Dealer Holdback	(35.5)	(43.4)
Payments of Dealer Holdback	(100.8)	(109.7)
Purchases of property and equipment	(6.9)	(3.6)
Net cash used in investing activities	(689.3)	(793.0)
Cash Flows From Financing Activities:
Borrowings under revolving secured line of credit	3,076.7	1,280.8
Repayments under revolving secured line of credit	(2,946.2)	(1,253.3)
Proceeds from secured financing	1,664.5	1,433.3
Repayments of secured financing	(1,396.8)	(1,019.0)
Payments of debt issuance costs	(9.1)	(6.3)
Repurchase of common stock	(123.5)	(40.8)
Excess tax benefits from stock-based compensation plans	0.0	27.2
Proceeds from (Payments for) Other Financing Activities	(0.6)	7.0
Net cash provided by financing activities	265.0	428.9
Net decrease in cash and cash equivalents	(9.7)	(0.6)
Cash and cash equivalents, beginning of period	14.6	6.3
Cash and cash equivalents, end of period	4.9	5.7
Supplemental Disclosure of Cash Flow Information:
Cash paid during the period for interest	88.9	73.5
Cash paid during the period for income taxes	$ 132.1	$ 75.2