SHAREHOLDERS' INTEREST - Changes in amounts included in our cumulative other comprehensive income (loss) by component (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Beginning balance	$ (1,212)	$ (1,393)
Other comprehensive income (loss) before reclassifications	(559)	124
Income taxes	207	(64)
Net other comprehensive income (loss) before reclassifications	(352)	60
Amounts reclassified from cumulative other comprehensive income (loss)(1)	162	187
Income taxes	(57)	(66)
Net amounts reclassified from cumulative other comprehensive income (loss)	105	121
Total other comprehensive income (loss)	(247)	181
Ending balance	(1,459)	(1,212)
Foreign currency translation adjustments
Beginning balance	207	304
Other comprehensive income (loss) before reclassifications	25	(97)
Income taxes	0	0
Net other comprehensive income (loss) before reclassifications	25	(97)
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)	25	(97)
Ending balance	232	207
Unrealized gains on available-for-sale securities
Beginning balance	6	6
Other comprehensive income (loss) before reclassifications	1	0
Income taxes	0	0
Net other comprehensive income (loss) before reclassifications	1	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)	1	0
Ending balance	7	6
Pension | Actuarial losses
Beginning balance	(1,372)	(1,623)
Other comprehensive income (loss) before reclassifications	(590)	184
Income taxes	208	(52)
Net other comprehensive income (loss) before reclassifications	(382)	132
Amounts reclassified from cumulative other comprehensive income (loss)(1)	156	182
Income taxes	(53)	(63)
Net amounts reclassified from cumulative other comprehensive income (loss)	103	119
Total other comprehensive income (loss)	(279)	251
Ending balance	(1,651)	(1,372)
Pension | Prior service credits (costs)
Beginning balance	(11)	(15)
Other comprehensive income (loss) before reclassifications	0	2
Income taxes	0	0
Net other comprehensive income (loss) before reclassifications	0	2
Amounts reclassified from cumulative other comprehensive income (loss)(1)	4	4
Income taxes	(2)	(2)
Net amounts reclassified from cumulative other comprehensive income (loss)	2	2
Total other comprehensive income (loss)	2	4
Ending balance	(9)	(11)
Other Postretirement Benefits | Actuarial losses
Beginning balance	(77)	(108)
Other comprehensive income (loss) before reclassifications	5	37
Income taxes	(1)	(12)
Net other comprehensive income (loss) before reclassifications	4	25
Amounts reclassified from cumulative other comprehensive income (loss)(1)	9	10
Income taxes	(3)	(4)
Net amounts reclassified from cumulative other comprehensive income (loss)	6	6
Total other comprehensive income (loss)	10	31
Ending balance	(67)	(77)
Other Postretirement Benefits | Prior service credits (costs)
Beginning balance	35	43
Other comprehensive income (loss) before reclassifications	0	(2)
Income taxes	0	0
Net other comprehensive income (loss) before reclassifications	0	(2)
Amounts reclassified from cumulative other comprehensive income (loss)(1)	(7)	(9)
Income taxes	1	3
Net amounts reclassified from cumulative other comprehensive income (loss)	(6)	(6)
Total other comprehensive income (loss)	(6)	(8)
Ending balance	$ 29	$ 35