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	315			315
Other comprehensive income	(3)				(3)
Dividends declared on common stock	(210)			(210)
Issuances of common stock (in shares)		637,000
Issuances of common stock	12	$ 2	10
Stock Repurchased During Period, Shares		(6,000)
Stock Repurchased During Period, Value	0	$ 0	0
Share-based compensation	(7)		(5)	(2)
Balance (in shares) at Mar. 31, 2019		514,668,000
Ending balance at Mar. 31, 2019	$ 12,329	$ 1,287	6,173	4,996	(127)
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	295			295
Other comprehensive income	(7)				(7)
Dividends declared on common stock	(227)			(227)
Issuances of common stock (in shares)		495,000
Issuances of common stock	12	$ 2	10
Share-based compensation	(8)		(7)	(1)
Adoption of ASC Topic 326	$ (2)			(2)
Balance (in shares) at Mar. 31, 2020	525,033,594	525,034,000
Ending balance at Mar. 31, 2020	$ 13,302	$ 1,313	$ 6,659	$ 5,478	$ (148)