CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Common Stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Balance (in shares) at Dec. 31, 2018		514,037,000
Beginning balance at Dec. 31, 2018	$ 12,222	$ 1,285	$ 6,168	$ 4,893	$ (124)
Increase (Decrease) in Stockholders' Equity
Net income	553			553
Other comprehensive income	(11)				(11)
Dividends declared on common stock (USD per share)		$ 0.81
Dividends declared on common stock	(419)			(419)
Issuances of common stock (in shares)		834,000
Issuances of common stock	22	$ 2	20
Stock Repurchased During Period, Shares		(6,000)
Stock Repurchased During Period, Value	0	$ 0	0
Share-based compensation	(1)		2	(3)
Balance (in shares) at Jun. 30, 2019		514,865,000
Ending balance at Jun. 30, 2019	12,366	$ 1,287	6,190	5,024	(135)
Balance (in shares) at Mar. 31, 2019		514,668,000
Beginning balance at Mar. 31, 2019	12,329	$ 1,287	6,173	4,996	(127)
Increase (Decrease) in Stockholders' Equity
Net income	238			238
Other comprehensive income	(8)				(8)
Dividends declared on common stock (USD per share)		$ 0.41
Dividends declared on common stock	(209)			(209)
Issuances of common stock (in shares)		197,000
Issuances of common stock	10	$ 0	10
Share-based compensation	6		7	(1)
Balance (in shares) at Jun. 30, 2019		514,865,000
Ending balance at Jun. 30, 2019	$ 12,366	$ 1,287	6,190	5,024	(135)
Balance (in shares) at Dec. 31, 2019	524,539,000	524,539,000
Beginning balance at Dec. 31, 2019	$ 13,239	$ 1,311	6,656	5,413	(141)
Increase (Decrease) in Stockholders' Equity
Net income	582			582
Other comprehensive income	(4)				(4)
Dividends declared on common stock (USD per share)		$ 0.86
Dividends declared on common stock	(453)			(453)
Issuances of common stock (in shares)		666,000
Issuances of common stock	23	$ 2	21
Share-based compensation	0		2	(2)
Adoption of ASC Topic 326	$ (2)			(2)
Balance (in shares) at Jun. 30, 2020	525,204,978	525,205,000
Ending balance at Jun. 30, 2020	$ 13,385	$ 1,313	6,679	5,538	(145)
Balance (in shares) at Mar. 31, 2020		525,034,000
Beginning balance at Mar. 31, 2020	13,302	$ 1,313	6,659	5,478	(148)
Increase (Decrease) in Stockholders' Equity
Net income	287			287
Other comprehensive income	3				3
Dividends declared on common stock (USD per share)		$ 0.43
Dividends declared on common stock	(226)			(226)
Issuances of common stock (in shares)		171,000
Issuances of common stock	11	$ 0	11
Share-based compensation	$ 8		9	(1)
Balance (in shares) at Jun. 30, 2020	525,204,978	525,205,000
Ending balance at Jun. 30, 2020	$ 13,385	$ 1,313	$ 6,679	$ 5,538	$ (145)