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	1,080			1,080
Other comprehensive income	(18)				(18)
Dividends declared on common stock (USD per share)		$ 1.215
Dividends declared on common stock	(633)			(633)
Issuances of common stock (in shares)		10,353,000
Issuances of common stock	484	$ 26	458
Stock Repurchased During Period, Shares		(6,000)
Stock Repurchased During Period, Value	0	$ 0	0
Share-based compensation	6		10	(4)
Balance (in shares) at Sep. 30, 2019		524,384,000
Ending balance at Sep. 30, 2019	13,141	$ 1,311	6,636	5,336	(142)
Increase (Decrease) in Stockholders' Equity
Net current period other comprehensive income (loss)					(18)
Balance (in shares) at Jun. 30, 2019		514,865,000
Beginning balance at Jun. 30, 2019	12,366	$ 1,287	6,190	5,024	(135)
Increase (Decrease) in Stockholders' Equity
Net income	527			527
Other comprehensive income	(7)				(7)
Dividends declared on common stock (USD per share)		$ 0.405
Dividends declared on common stock	(214)			(214)
Issuances of common stock (in shares)		9,519,000
Issuances of common stock	462	$ 24	438
Share-based compensation	7		8	(1)
Balance (in shares) at Sep. 30, 2019		524,384,000
Ending balance at Sep. 30, 2019	$ 13,141	$ 1,311	6,636	5,336	(142)
Increase (Decrease) in Stockholders' Equity
Net current period other comprehensive income (loss)					(7)
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	1,185			1,185
Other comprehensive income	(2)				(2)
Dividends declared on common stock (USD per share)		$ 1.29
Dividends declared on common stock	(679)			(679)
Issuances of common stock (in shares)		968,000
Issuances of common stock	33	$ 3	30
Stock Repurchased During Period, Shares		(54,000)
Stock Repurchased During Period, Value	(4)	$ 0	(4)
Share-based compensation	7		12	(5)
Adoption of ASC Topic 326	$ (2)			(2)
Balance (in shares) at Sep. 30, 2020	525,452,824	525,453,000
Ending balance at Sep. 30, 2020	$ 13,777	$ 1,314	6,694	5,912	(143)
Increase (Decrease) in Stockholders' Equity
Net current period other comprehensive income (loss)					(2)
Balance (in shares) at Jun. 30, 2020		525,205,000
Beginning balance at Jun. 30, 2020	13,385	$ 1,313	6,679	5,538	(145)
Increase (Decrease) in Stockholders' Equity
Net income	603			603
Other comprehensive income	2				2
Dividends declared on common stock (USD per share)		$ 0.43
Dividends declared on common stock	(226)			(226)
Issuances of common stock (in shares)		302,000
Issuances of common stock	10	$ 1	9
Stock Repurchased During Period, Shares		(54,000)
Stock Repurchased During Period, Value	(4)	$ 0	(4)
Share-based compensation	$ 7		10	(3)
Balance (in shares) at Sep. 30, 2020	525,452,824	525,453,000
Ending balance at Sep. 30, 2020	$ 13,777	$ 1,314	$ 6,694	$ 5,912	(143)
Increase (Decrease) in Stockholders' Equity
Net current period other comprehensive income (loss)					$ 2