SECURED BORROWINGS - Schedule of Average Borrowings Outstanding (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Disclosure Of Repurchase Agreements [Abstract]
Average borrowings for the effects of related derivatives held as cash flow hedges	$ 12,549,893	$ 12,380,375
Effective borrowing rate considering cash flow hedges	1.17%	0.89%