GEOGRAPHIC AREAS - Long-Lived Assets by Geographic Area (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 14,349	$ 14,998
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	14,074	14,778
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 275	$ 220