SHAREHOLDERS' INTEREST - Changes in amounts included in our cumulative other comprehensive income (loss) by component (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Beginning balance	$ (1,393)	$ (686)
Other comprehensive income (loss) before reclassifications	124	(1,075)
Income taxes	(64)	377
Net other comprehensive income (loss) before reclassifications	60	(698)
Amounts reclassified from cumulative other comprehensive income (loss)(1)	187	(19)
Income taxes	(66)	10
Net amounts reclassified from cumulative other comprehensive income (loss)	121	(9)
Total other comprehensive income (loss)	181	(707)
Ending balance	(1,212)	(1,393)
Foreign currency translation adjustments
Beginning balance	304	354
Other comprehensive income (loss) before reclassifications	(97)	(50)
Income taxes	0	0
Net other comprehensive income (loss) before reclassifications	(97)	(50)
Amounts reclassified from cumulative other comprehensive income (loss)(1)	0	0
Income taxes	0	0
Net amounts reclassified from cumulative other comprehensive income (loss)	0	0
Total other comprehensive income (loss)	(97)	(50)
Ending balance	207	304
Unrealized gains on available-for-sale securities
Beginning balance	6	6
Other comprehensive income (loss) before reclassifications	0	0
Income taxes	0	0
Net other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from cumulative other comprehensive income (loss)(1)	0	0
Income taxes	0	0
Net amounts reclassified from cumulative other comprehensive income (loss)	0	0
Total other comprehensive income (loss)	0	0
Ending balance	6	6
Pension | Actuarial losses
Beginning balance	(1,623)	(1,066)
Other comprehensive income (loss) before reclassifications	184	(1,008)
Income taxes	(52)	369
Net other comprehensive income (loss) before reclassifications	132	(639)
Amounts reclassified from cumulative other comprehensive income (loss)(1)	182	125
Income taxes	(63)	(43)
Net amounts reclassified from cumulative other comprehensive income (loss)	119	82
Total other comprehensive income (loss)	251	(557)
Ending balance	(1,372)	(1,623)
Pension | Prior service credits (costs)
Beginning balance	(15)	(19)
Other comprehensive income (loss) before reclassifications	2	1
Income taxes	0	0
Net other comprehensive income (loss) before reclassifications	2	1
Amounts reclassified from cumulative other comprehensive income (loss)(1)	4	5
Income taxes	(2)	(2)
Net amounts reclassified from cumulative other comprehensive income (loss)	2	3
Total other comprehensive income (loss)	4	4
Ending balance	(11)	(15)
Other Postretirement Benefits | Actuarial losses
Beginning balance	(108)	(111)
Other comprehensive income (loss) before reclassifications	37	(6)
Income taxes	(12)	1
Net other comprehensive income (loss) before reclassifications	25	(5)
Amounts reclassified from cumulative other comprehensive income (loss)(1)	10	12
Income taxes	(4)	(4)
Net amounts reclassified from cumulative other comprehensive income (loss)	6	8
Total other comprehensive income (loss)	31	3
Ending balance	(77)	(108)
Other Postretirement Benefits | Prior service credits (costs)
Beginning balance	43	150
Other comprehensive income (loss) before reclassifications	(2)	(12)
Income taxes	0	7
Net other comprehensive income (loss) before reclassifications	(2)	(5)
Amounts reclassified from cumulative other comprehensive income (loss)(1)	(9)	(161)
Income taxes	3	59
Net amounts reclassified from cumulative other comprehensive income (loss)	(6)	(102)
Total other comprehensive income (loss)	(8)	(107)
Ending balance	$ 35	$ 43