Quarterly Financial Information Restatement of 2019 Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended																6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Net income (loss)							$ 193								$ 100		$ 409	$ 270	$ 652	$ 421	$ 860		$ 622		$ 366
Adjustments to reconcile net income (loss) to net cash provided by (used for) operating activities:
Depreciation, amortization and accretion			$ 388		$ 393		394		$ 389		$ 385		$ 379		374		787	753	1,175	1,138	1,572		1,527		1,241
(Gains) losses on retirement of long-term obligations	$ 0	[1]	0	[1]	1	[1]	1	[1]	0	[1]	32	[1]	3	[1]	71	[1]	2	74	2	106	2	[2]	106	[2]	4	[3]
Amortization of deferred financing costs and other non-cash interest							1								2		1	4	1	5	1		7		9
Stock-based compensation expense							29								23		62	47	91	79	117		103		92
Asset write-down charges			2		6		6		8		8		6		3		12	9	13	18	19		26		17
Deferred income tax (benefit) provision							1								1		1	1	2	2	2		2		15
Other non-cash adjustments, net							2								2		3	1	4	2	(2)		2		(2)
Changes in assets and liabilities, excluding the effects of acquisitions:
Increase (decrease) in accrued interest							(41)								(28)		18	22	(38)	(31)	21		16		35
Increase (decrease) in accounts payable							(5)								(5)		6	3	37	31	19		37		(34)
Increase (decrease) in other liabilities							(7)								(43)		77	76	179	179	254		271		234
Decrease (increase) in receivables							(43)								(5)		(89)	(59)	(166)	(74)	(96)		(105)		71
Decrease (increase) in other assets							(19)								(43)		(62)	(91)	(62)	(103)	(71)		(114)		(16)
Net Cash Provided by (Used in) Operating Activities							512								452		1,227	1,110	1,890	1,773	2,698		2,500		2,032
Cash flows from investing activities:
Capital expenditures							(480)								(370)		(998)	(762)	(1,537)	(1,239)	(2,057)		(1,739)		(1,217)
Payments for acquisitions, net of cash acquired							(10)								(14)		(13)	(18)	(15)	(26)	(17)		(42)		(9,260)
Other investing activities, net							1								0		1	3	3	(14)	(7)		(12)		(5)
Net Cash Provided by (Used in) Investing Activities							(489)								(384)		(1,010)	(777)	(1,549)	(1,279)	(2,081)		(1,793)		(10,482)
Cash flows from financing activities:
Proceeds from issuance of long-term debt							996								1,743		995	1,743	1,895	2,743	1,894		2,742		3,093
Principal payments on debt and other long-term obligations							(25)								(32)		(36)	(47)	(59)	(76)	(86)		(105)		(119)
Purchases and redemptions of long-term debt							(12)								(1,318)		(12)	(1,318)	(12)	(2,346)	(12)		(2,346)		0
Borrowings under revolving credit facility							710								170		1,195	485	1,585	1,290	2,110		1,820		2,820
Payments under revolving credit facility							(1,140)								(1,050)		(1,785)	(1,150)	(2,270)	(1,465)	(2,660)		(1,725)		(1,840)
Proceeds from Issuance of Commercial Paper							0										500		0		155		0
Payments for financing costs							(10)								(15)		(14)	(20)	(24)	(33)	(24)		(31)		(29)
Net proceeds from issuance of common stock															843			841		841	0		841		4,221
Net proceeds from issuance of preferred stock																					0		0		1,608
Purchases of common stock							(42)								(33)		(43)	(34)	(44)	(34)	(44)		(34)		(23)
Dividends/distributions paid on common stock							(477)								(443)		(944)	(879)	(1,415)	(1,315)	(1,912)		(1,782)		(1,509)
Dividends paid on preferred stock							(28)								(28)		(57)	(57)	(85)	(85)	(113)		(113)		(30)
Net Cash Provided by (Used in) Financing Activities							(28)								(163)		(201)	(436)	(429)	(480)	(692)		(733)		8,192
Net Cash Provided by (Used in) Continuing Operations							(5)								(95)		16	(103)	(88)	14	(75)		(26)		(258)
Effect of exchange rate changes on cash							0								0		0	(1)	0	(1)	0		(1)		1
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	325		429		408		413		453		336		345		440		413	440	413	440	413		440		697
Cash, Cash Equivalents and Restricted Cash - End of Period	338		325		429		408		413		453		336		345		429	336	325	453	338		413		440
Previously Reported [Member]
Net income (loss)							210								114		456	294	729	458			671		445
Adjustments to reconcile net income (loss) to net cash provided by (used for) operating activities:
Depreciation, amortization and accretion			389						390										1,176				1,528		1,242
Changes in assets and liabilities, excluding the effects of acquisitions:
Increase (decrease) in other liabilities							(24)								(57)		30	53	102	144			223		175
Decrease (increase) in receivables																									61
Net Cash Provided by (Used in) Operating Activities							512								452		1,227	1,111	1,891	1,775			2,502		2,043
Cash flows from investing activities:
Capital expenditures																		(763)	(1,538)	(1,241)			(1,741)		(1,228)
Net Cash Provided by (Used in) Investing Activities																		(778)	(1,550)	(1,281)			(1,795)		(10,493)
Cash flows from financing activities:
Net Cash Provided by (Used in) Continuing Operations							(5)								(95)		16	(103)	(88)	14			(26)		(258)
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	325		429		408		413		453		336		345		440		413	440	413	440	413		440		697
Cash, Cash Equivalents and Restricted Cash - End of Period			325		429		408		413		453		336		345		429	336	325	453			413		440
Restatement Adjustment [Member]
Net income (loss)							(17)		(13)						(14)		(47)	(23)	(77)	(35)			(48)		(59)
Adjustments to reconcile net income (loss) to net cash provided by (used for) operating activities:
Depreciation, amortization and accretion			0						0										0				0		0
Changes in assets and liabilities, excluding the effects of acquisitions:
Increase (decrease) in other liabilities							17								14		47	23	77	35			48		59
Decrease (increase) in receivables																									0
Net Cash Provided by (Used in) Operating Activities							0								0		0	0	0	0			0		0
Cash flows from investing activities:
Capital expenditures																		0	0	0			0		0
Net Cash Provided by (Used in) Investing Activities																		0	0	0			0		0
Cash flows from financing activities:
Net Cash Provided by (Used in) Continuing Operations							0								0		0	0	0	0			0		0
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	$ 0		0		0		0		0		0		0		0		0	0	0	0	0		0		0
Cash, Cash Equivalents and Restricted Cash - End of Period			0		0		0		0		0		0		0		0	0	0	0			0		0
Other Adjustments [Domain]
Net income (loss)							0		1						0		0	(1)	0	(2)			(1)		(20)
Adjustments to reconcile net income (loss) to net cash provided by (used for) operating activities:
Depreciation, amortization and accretion			(1)						(1)										(1)				(1)		(1)
Changes in assets and liabilities, excluding the effects of acquisitions:
Increase (decrease) in other liabilities							0								0		0	0		0			0		0
Decrease (increase) in receivables																									10
Net Cash Provided by (Used in) Operating Activities							0								0		0	(1)	(1)	(2)			(2)		(11)
Cash flows from investing activities:
Capital expenditures																		1	1	2			2		11
Net Cash Provided by (Used in) Investing Activities																		1	1	2			2		11
Cash flows from financing activities:
Net Cash Provided by (Used in) Continuing Operations							0								0		0	0		0			0		0
Cash, Cash Equivalents and Restricted Cash - Beginning of Period			$ 0		0		0		0		0		0		0		0	0	$ 0	0	$ 0		0		0
Cash, Cash Equivalents and Restricted Cash - End of Period					$ 0		$ 0		$ 0		$ 0		$ 0		$ 0		$ 0	$ 0		$ 0			$ 0		$ 0

[1] The sum of quarterly information may not agree to year-to-date information due to rounding.

[2] Inclusive of the write-off of the respective deferred financing costs.

[3] The losses represent write-off of deferred financing costs.