SECURED BORROWINGS - Schedule of Average Borrowings Outstanding (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Dec. 31, 2017 |
|
| Disclosure Of Repurchase Agreements [Abstract] | ||
| Average borrowings for the effects of related derivatives held as cash flow hedges | $ 12,235,554 | $ 12,408,550 |
| Effective borrowing rate considering cash flow hedges | 1.47% | 1.29% |