GEOGRAPHIC AREAS - Long-Lived Assets by Geographic Area (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 9,301	$ 9,324	$ 9,438
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	8,187	8,069	8,116
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	460	579	652
Other foreign countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 654	$ 676	$ 670