Consolidated Statements of Equity - USD ($) $ in Millions	Total	Common Stock Shares	Common Stock Amount	Accumulated Other Comprehensive Loss	Retained Earnings
Balance, shares at Dec. 31, 2017		89,114,265
Balance at Dec. 31, 2017	$ 2,416		$ 1,207	$ (8)	$ 1,217
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued pursuant to equity-based plans		153,694
Proceeds from issuance of shares pursuant to equity-based plans	1		1
Stock-based compensation	$ 4		4	0	0
Common Stock, Dividends, Per Share, Declared	$ 1.4275
Dividends declared	$ (128)		0	0	(128)
Net income	212		0	0	212
Other comprehensive income (loss)	1		0	1	0
Balance, shares at Dec. 31, 2018		89,267,959
Balance at Dec. 31, 2018	2,506		1,212	(7)	1,301
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued pursuant to equity-based plans		119,165
Proceeds from issuance of shares pursuant to equity-based plans	1		1
Stock-based compensation	$ 7		7	0	0
Common Stock, Dividends, Per Share, Declared	$ 1.5175
Dividends declared	$ (136)		0	0	(136)
Net income	214		0	0	214
Reclassification of stranded tax effects due to Tax Reform				2	(2)
Other comprehensive income (loss)	(1)		0	(1)	0
Balance, shares at Dec. 31, 2019		89,387,124
Balance at Dec. 31, 2019	2,591		1,220	(10)	1,381
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued pursuant to equity-based plans		150,207
Proceeds from issuance of shares pursuant to equity-based plans	2		2
Stock-based compensation	$ 9		9	0	0
Common Stock, Dividends, Per Share, Declared	$ 1.5850
Dividends declared	$ (143)		0	0	(143)
Net income	155		0	0	155
Other comprehensive income (loss)	(1)		0	(1)	0
Balance, shares at Dec. 31, 2020		89,537,331
Balance at Dec. 31, 2020	$ 2,613		$ 1,231	$ (11)	$ 1,393