Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows From Operating Activities:
Net income	$ 120.1	$ 93.3
Adjustments to reconcile cash provided by operating activities:
Provision for credit losses	23.4	20.5
Depreciation	1.3	1.6
Amortization	2.9	2.5
Provision for deferred income taxes	19.1	40.3
Stock-based compensation	3.1	2.5
Change in operating assets and liabilities:
Increase (decrease) in accounts payable and accrued liabilities	19.1	(10.1)
Increase in income taxes receivable	(0.3)	(0.9)
Increase in income taxes payable	15.7	9.3
Decrease in other assets	3.0	2.9
Net cash provided by operating activities	207.4	161.9
Cash Flows From Investing Activities:
Purchases of restricted securities available for sale	(13.7)	(13.9)
Proceeds from sale of restricted securities available for sale	6.7	9.2
Maturities of restricted securities available for sale	1.4	3.4
Principal collected on Loans receivable	643.9	567.0
Advances to Dealers	(709.2)	(536.9)
Purchases of Consumer Loans	(342.4)	(254.6)
Accelerated payments of Dealer Holdback	(12.6)	(10.2)
Payments of Dealer Holdback	(33.2)	(35.2)
Purchases of property and equipment	(1.2)	(3.2)
Net cash used in investing activities	(460.3)	(274.4)
Cash Flows From Financing Activities:
Borrowings under revolving secured line of credit	465.4	622.9
Repayments under revolving secured line of credit	(456.3)	(488.8)
Proceeds from secured financing	1,000.0	736.0
Repayments of secured financing	(632.2)	(568.0)
Payments of debt issuance costs	(3.9)	(2.8)
Repurchase of common stock	(2.0)	(105.8)
Other financing activities	(1.9)	7.5
Net cash provided by financing activities	369.1	201.0
Net increase in cash, cash equivalents, restricted cash and restricted cash equivalents	116.2	88.5
Cash, cash equivalents, restricted cash and restricted cash equivalents end of period	380.0	327.8
Cash, cash equivalents, restricted cash and restricted cash equivalents beginning of period	263.8	239.3
Supplemental Disclosure of Cash Flow Information:
Cash paid during the period for interest	40.3	34.0
Cash paid during the period for income taxes	$ 1.6	$ 1.8