Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash Flows From Operating Activities:
Net income	$ 74.4	$ 71.5
Adjustments to reconcile cash provided by operating activities:
Provision for credit losses	22.1	6.2
Depreciation	1.6	1.5
Amortization	2.2	2.2
Loss on retirement of property and equipment	0.0	0.1
Provision for deferred income taxes	3.3	7.0
Stock-based compensation	2.1	4.1
Change in operating assets and liabilities:
Increase (decrease) in accounts payable and accrued liabilities	(6.3)	7.9
Decrease (increase) in income taxes receivable	(9.8)	0.4
Decrease in income taxes payable	0.0	13.0
Decrease in other assets	2.1	3.5
Net cash provided by operating activities	91.7	117.4
Cash Flows From Investing Activities:
Increase in restricted cash and cash equivalents	(58.3)	(41.3)
Purchases of restricted securities available for sale	(12.6)	(11.6)
Proceeds from sale of restricted securities available for sale	11.1	11.5
Maturities of restricted securities available for sale	1.2	0.5
Principal collected on Loans receivable	514.8	454.5
Advances to Dealers	(562.7)	(533.5)
Purchases of Consumer Loans	(181.4)	(92.6)
Accelerated payments of Dealer Holdback	(14.8)	(13.8)
Payments of Dealer Holdback	(39.9)	(41.1)
Purchases of property and equipment	(1.7)	(1.3)
Net cash used in investing activities	(344.3)	(268.7)
Cash Flows From Financing Activities:
Borrowings under revolving secured line of credit	798.7	988.4
Repayments under revolving secured line of credit	(820.1)	(1,107.9)
Proceeds from secured financing	661.1	535.4
Repayments of secured financing	(380.4)	(433.1)
Proceeds from issuance of senior notes	0.0	248.2
Payments of debt issuance costs	(0.7)	(6.2)
Repurchase of common stock	(40.8)	(1.1)
Tax benefits from stock-based compensation plans	27.2	0.3
Proceeds from (Payments for) Other Financing Activities	10.4	7.6
Net cash provided by financing activities	255.4	231.6
Net increase in cash and cash equivalents	2.8	80.3
Cash and cash equivalents, beginning of period	6.3	6.4
Cash and cash equivalents, end of period	9.1	86.7
Supplemental Disclosure of Cash Flow Information:
Cash paid during the period for interest	29.2	17.3
Cash paid during the period for income taxes	$ 22.0	$ 20.2