General - Additional Information (Details) - USD ($)		3 Months Ended	9 Months Ended
	Jan. 01, 2020	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Jul. 01, 2019	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018	Jul. 01, 2018	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impairment of intangible assets		$ 55,000,000	$ 55,000,000	$ 0
Lease liabilities		542,000,000	542,000,000
Right-of-Use asset		$ 443,000,000	$ 443,000,000
Operating lease, renewal term		20 years	20 years
Operating lease, option to terminate			60 days
Lease, cost		$ 45,000,000	$ 128,000,000
Variable lease, cost		7,000,000	22,000,000
Stockholders' equity		(26,140,000,000)	(26,140,000,000)	(23,659,000,000)				$ (21,312,000,000)
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease liabilities							$ 585,000,000
Right-of-Use asset							488,000,000
Retained income
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					$ 0		21,000,000		$ 0		$ 1,088,000,000
Stockholders' equity		(46,527,000,000)	(46,527,000,000)	(44,776,000,000)		$ (45,803,000,000)		(44,033,000,000)		$ (43,997,000,000)		$ (41,579,000,000)
Retained income | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle							21,000,000
Accumulated other comprehensive income (loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					0		0		0		(910,000,000)
Stockholders' equity		$ (2,107,000,000)	$ (2,107,000,000)	(144,000,000)		(1,760,000,000)		(118,000,000)		(243,000,000)		(1,889,000,000)
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, term of contract		1 year	1 year
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, term of contract		10 years	10 years
Impact of change | Impact of change
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity		$ 397,000,000	$ 397,000,000	(26,000,000)	12,000,000		18,000,000				0
Impact of change | Impact of change | Retained income
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					0		0		0		0
Stockholders' equity		1,879,000,000	1,879,000,000	1,402,000,000		1,739,000,000		1,675,000,000		1,511,000,000	1,580,000,000	1,583,000,000
Impact of change | Impact of change | Accumulated other comprehensive income (loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					$ 0		$ 0		$ 0		0
Stockholders' equity		$ (1,482,000,000)	$ (1,482,000,000)	$ (1,428,000,000)		$ (1,512,000,000)		$ (1,675,000,000)		$ (1,511,000,000)	$ (1,580,000,000)	$ (1,583,000,000)
Forecast | Minimum | Retained income | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle	$ (75,000,000)
Allowance for credit loss, period increase	260,000,000
Forecast | Maximum | Retained income | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle	(125,000,000)
Allowance for credit loss, period increase	$ 330,000,000