GEOGRAPHIC AREAS - Long-Lived Assets by Geographic Area (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 15,145	$ 16,433	$ 9,374
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	14,922	15,700	8,260
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	223	206	460
Other foreign countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 0	$ 527	$ 654