Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash Flows From Operating Activities:
Net income	$ 245.2	$ 219.7
Adjustments to reconcile cash provided by operating activities:
Provision for credit losses	62.8	27.8
Depreciation	4.7	4.3
Amortization	6.8	6.4
Loss on retirement of property and equipment	0.1	0.3
Provision for deferred income taxes	32.0	23.1
Stock-based compensation	5.6	10.0
Change in operating assets and liabilities:
Increase (decrease) in accounts payable and accrued liabilities	(0.9)	5.2
Decrease in income taxes receivable	4.6	1.1
Increase (decrease) in income taxes payable	2.0	(0.6)
Decrease in other assets	0.6	3.0
Net cash provided by operating activities	363.5	300.3
Cash Flows From Investing Activities:
Increase in restricted cash and cash equivalents	(65.4)	(18.4)
Purchases of restricted securities available for sale	(28.3)	(26.6)
Proceeds from sale of restricted securities available for sale	25.5	26.0
Maturities of restricted securities available for sale	4.5	3.2
Principal collected on Loans receivable	1,493.2	1,318.7
Advances to Dealers	(1,476.4)	(1,371.5)
Purchases of Consumer Loans	(589.4)	(266.8)
Accelerated payments of Dealer Holdback	43.4	39.6
Payments of Dealer Holdback	(109.7)	(115.2)
Purchases of property and equipment	(3.6)	(3.2)
Net cash used in investing activities	(793.0)	(493.4)
Cash Flows From Financing Activities:
Borrowings under revolving secured line of credit	1,280.8	1,463.1
Repayments under revolving secured line of credit	(1,253.3)	(1,582.6)
Proceeds from secured financing	1,433.3	1,196.0
Repayments of secured financing	(1,019.0)	(996.1)
Proceeds from issuance of senior notes	0.0	248.2
Payments of debt issuance costs	(6.3)	(11.0)
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	7.0	4.6
Net cash provided by financing activities	428.9	321.4
Net increase (decrease) in cash and cash equivalents	(0.6)	128.3
Cash and cash equivalents, beginning of period	6.3	6.4
Cash and cash equivalents, end of period	5.7	134.7
Supplemental Disclosure of Cash Flow Information:
Cash paid during the period for interest	73.5	52.3
Cash paid during the period for income taxes	$ 75.2	$ 102.2