Loans and Interest Receivable - Loans and Interest Receivables by FICO Score (Details) - Consumer Receivables - USD ($) $ in Millions |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Financing Receivable, Recorded Investment [Line Items] | ||
| Consumer loans and interest receivable | $ 6,401 | $ 4,996 |
| Greater Than 760 | ||
| Financing Receivable, Recorded Investment [Line Items] | ||
| Consumer loans and interest receivable | 832 | 665 |
| 680-759 | ||
| Financing Receivable, Recorded Investment [Line Items] | ||
| Consumer loans and interest receivable | 2,439 | 1,938 |
| 600-679 | ||
| Financing Receivable, Recorded Investment [Line Items] | ||
| Consumer loans and interest receivable | 2,378 | 1,840 |
| Less Than 599 | ||
| Financing Receivable, Recorded Investment [Line Items] | ||
| Consumer loans and interest receivable | $ 752 | $ 553 |