SIGNIFICANT ACCOUNTING POLICIES - New Accounting Pronouncements (Details) - USD ($) $ in Millions	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity	$ 11,643		$ 11,565	$ 12,359	$ 19,395
Retained Earnings
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity	$ (795)		2,145	$ 5,039	$ 8,860
Accounting Standards Update 2016-13 | Cumulative effect of period of adoption, adjusted balance | Retained Earnings
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity		$ (40)	$ (36)