Statement of Changes in Total Equity - USD ($) $ in Millions	Total	Shareholders' Equity [Member]	Common Stock [Member]	Additional Paid In Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]
Total Equity, beginning of period at Dec. 31, 2014	$ 10,789	$ 10,774	$ 74	$ 2,769	$ (936)	$ 10,289	$ (1,422)	$ 15
Increase (Decrease) In Stockholders Equity [Roll Forward]
Effect of issuing stock for employee benefit plans	62	62		55		(177)	184
Other comprehensive income (loss)	2	2			2
Net income (loss)	531	533				533		$ (2)
Common dividends declared (per share: $0.04)	(10)	(10)				(10)
Repurchase of common stock	(418)	(418)					(418)
Other transactions impacting noncontrolling interest	2	(1)		(1)				3
Total Equity, end of period at Mar. 31, 2015	10,958	10,942	74	2,823	(934)	10,635	(1,656)	16
Beginning Balance at Dec. 31, 2014	90
Redeemable Noncontrolling Interest [Roll Forward]
Other comprehensive income (loss)	$ (9)
Net income (loss)
Other transactions impacting noncontrolling interest	$ 2
Ending Balance at Mar. 31, 2015	83
Total Equity, beginning of period at Dec. 31, 2015	12,044	12,035	74	2,859	(1,250)	12,121	(1,769)	$ 9
Increase (Decrease) In Stockholders Equity [Roll Forward]
Effect of issuing stock for employee benefit plans	(15)	(15)		21		(89)	53
Other comprehensive income (loss)	262	262			262
Net income (loss)	515	519				519		$ (4)
Common dividends declared (per share: $0.04)	(10)	(10)				(10)
Repurchase of common stock	(110)	(110)					(110)
Other transactions impacting noncontrolling interest	(2)	(6)		(6)				4
Total Equity, end of period at Mar. 31, 2016	12,684	$ 12,675	$ 74	$ 2,874	$ (988)	$ 12,541	$ (1,826)	$ 9
Beginning Balance at Dec. 31, 2015	69
Redeemable Noncontrolling Interest [Roll Forward]
Other comprehensive income (loss)	3
Net income (loss)	(1)
Other transactions impacting noncontrolling interest	2
Ending Balance at Mar. 31, 2016	$ 73