Condensed Consolidating Financial Information (Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	$ 739	$ 971
Investing activities:
Capital investments	(877)	(1,008)
Proceeds from sale of property and equipment	42	9
Other	0	4
Net cash used in investing activities	(835)	(995)
Financing activities:
Intercompany activities	0	0
Payments on long-term debt	(43)	(1,191)
Payments on revolving credit facility	0	(1,122)
Borrowings under revolving credit facility	0	1,482
Change in bank drafts outstanding	(11)	10
Debt issuance costs	0	(9)
Purchase of treasury stock	(21)	(25)
Preferred stock dividend	0	(27)
Cash paid for tax withholding	(1)	(1)
Net cash used in financing activities	(76)	(883)
Decrease in cash and cash equivalents	(172)	(907)
Cash and cash equivalents at beginning of year	201	916
Cash and cash equivalents at end of period	29	9
Parent
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	1,154	57
Investing activities:
Capital investments	0	(12)
Proceeds from sale of property and equipment	0	0
Other		4
Net cash used in investing activities	0	(8)
Financing activities:
Intercompany activities	(1,250)	(71)
Payments on long-term debt	(43)	(1,191)
Payments on revolving credit facility		(1,122)
Borrowings under revolving credit facility		1,482
Change in bank drafts outstanding	(11)	10
Debt issuance costs		(9)
Purchase of treasury stock	(21)	(25)
Preferred stock dividend		(27)
Cash paid for tax withholding	(1)	(1)
Net cash used in financing activities	(1,326)	(954)
Decrease in cash and cash equivalents	(172)	(905)
Cash and cash equivalents at beginning of year	201	914
Cash and cash equivalents at end of period	29	9
Guarantors
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	404	1,396
Investing activities:
Capital investments	(875)	(996)
Proceeds from sale of property and equipment	42	9
Other		0
Net cash used in investing activities	(833)	(987)
Financing activities:
Intercompany activities	429	(411)
Payments on long-term debt	0	0
Payments on revolving credit facility		0
Borrowings under revolving credit facility		0
Change in bank drafts outstanding	0	0
Debt issuance costs		0
Purchase of treasury stock	0	0
Preferred stock dividend		0
Cash paid for tax withholding	0	0
Net cash used in financing activities	429	(411)
Decrease in cash and cash equivalents	0	(2)
Cash and cash equivalents at beginning of year	0	2
Cash and cash equivalents at end of period	0	0
Non-Guarantors
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	0	0
Investing activities:
Capital investments	(2)	0
Proceeds from sale of property and equipment	0	0
Other		0
Net cash used in investing activities	(2)	0
Financing activities:
Intercompany activities	2	0
Payments on long-term debt	0	0
Payments on revolving credit facility		0
Borrowings under revolving credit facility		0
Change in bank drafts outstanding	0	0
Debt issuance costs		0
Purchase of treasury stock	0	0
Preferred stock dividend		0
Cash paid for tax withholding	0	0
Net cash used in financing activities	2	0
Decrease in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of year	0	0
Cash and cash equivalents at end of period	0	0
Eliminations
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(819)	(482)
Investing activities:
Capital investments	0	0
Proceeds from sale of property and equipment	0
Other		0
Net cash used in investing activities	0	0
Financing activities:
Intercompany activities	819	482
Payments on long-term debt	0	0
Payments on revolving credit facility		0
Borrowings under revolving credit facility		0
Change in bank drafts outstanding	0	0
Debt issuance costs		0
Purchase of treasury stock	0	0
Preferred stock dividend		0
Cash paid for tax withholding	0	0
Net cash used in financing activities	819	482
Decrease in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of year	0	0
Cash and cash equivalents at end of period	$ 0	$ 0