CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	ACCUMULATED OTHER COMPREHENSIVE LOSS	RETAINED EARNINGS
Increase (Decrease) in Stockholders' Equity
Cumulative effect of adoption of ASU | Accounting Standards Update 2018-02				$ 0	$ 0
Cumulative effect of adoption of ASU | Accounting Standards Update 2014-09					0
Cumulative effect of adoption of ASU | Accounting Standards Update 2016-09					3
Balance at beginning of period at Dec. 31, 2016		$ 547	$ 14,970	(2,117)	(1)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		3	5
Shares withheld to satisfy tax withholdings			(16)
Share-based compensation and other, net			59
Dividends declared			(648)		(240)
Acquisition of additional minority interest in a subsidiary			0
Other comprehensive income	$ 123			123
Net income	272				272
Balance at end of period at Sep. 30, 2017	$ 12,960	550	14,370	(1,994)	34
Increase (Decrease) in Stockholders' Equity
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 1.62
Cumulative effect of adoption of ASU | Accounting Standards Update 2018-02				0	0
Cumulative effect of adoption of ASU | Accounting Standards Update 2014-09					0
Cumulative effect of adoption of ASU | Accounting Standards Update 2016-09					0
Balance at beginning of period at Jun. 30, 2017		550	14,637	(2,050)	(51)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		0	2
Shares withheld to satisfy tax withholdings			(1)
Share-based compensation and other, net			21
Dividends declared			(289)		(7)
Acquisition of additional minority interest in a subsidiary			0
Other comprehensive income	$ 56			56
Net income	92				92
Balance at end of period at Sep. 30, 2017	$ 12,960	550	14,370	(1,994)	34
Increase (Decrease) in Stockholders' Equity
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.54
Cumulative effect of adoption of ASU	$ (407)
Cumulative effect of adoption of ASU | Accounting Standards Update 2018-02				(407)	407
Cumulative effect of adoption of ASU | Accounting Standards Update 2014-09					346
Cumulative effect of adoption of ASU | Accounting Standards Update 2016-09					0
Balance at beginning of period at Dec. 31, 2017	23,491	1,069	23,314	(1,995)	1,103
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		12	(2)
Shares withheld to satisfy tax withholdings			(50)
Share-based compensation and other, net			142
Dividends declared			0		(1,758)
Acquisition of additional minority interest in a subsidiary			(5)
Other comprehensive income	(52)			(52)
Net income	679				679
Balance at end of period at Sep. 30, 2018	$ 22,803	1,081	23,399	(2,454)	777
Increase (Decrease) in Stockholders' Equity
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 1.62
Cumulative effect of adoption of ASU | Accounting Standards Update 2018-02				0	0
Cumulative effect of adoption of ASU | Accounting Standards Update 2014-09					49
Cumulative effect of adoption of ASU | Accounting Standards Update 2016-09					0
Balance at beginning of period at Jun. 30, 2018		1,079	23,360	(2,490)	1,040
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		2	7
Shares withheld to satisfy tax withholdings			(15)
Share-based compensation and other, net			48
Dividends declared			0		(584)
Acquisition of additional minority interest in a subsidiary			(1)
Other comprehensive income	$ 36			36
Net income	272				272
Balance at end of period at Sep. 30, 2018	$ 22,803	$ 1,081	$ 23,399	$ (2,454)	$ 777
Increase (Decrease) in Stockholders' Equity
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.54