Employee Benefit Plans, Fair Value of Pension Plan Assets (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity Securities [Member]
Employee Benefit Plans (Textual)
Percentage of target allocations for plan assets		70.00%
Fixed Income Investments [Member]
Employee Benefit Plans (Textual)
Percentage of target allocations for plan assets		30.00%
Pension Plans [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[1]	$ 3,067	$ 2,709	$ 2,236
Pension Plans [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		1,103	1,145
Pension Plans [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		1,964	1,564
Pension Plans [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Equity Securities [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[2]	682	832
Pension Plans [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[2]	682	831
Pension Plans [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[2]	0	1
Pension Plans [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[2]	0	0
Pension Plans [Member] | Mutual Fund [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		244	213
Pension Plans [Member] | Mutual Fund [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		244	213
Pension Plans [Member] | Mutual Fund [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Mutual Fund [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Corporate Debt Instruments [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[2]	297	293
Pension Plans [Member] | Corporate Debt Instruments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[2]	0	0
Pension Plans [Member] | Corporate Debt Instruments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[2]	297	293
Pension Plans [Member] | Corporate Debt Instruments [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[2]	0	0
Pension Plans [Member] | Government Securities [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		227	201
Pension Plans [Member] | Government Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		85	53
Pension Plans [Member] | Government Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		142	148
Pension Plans [Member] | Government Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Defined Benefit Plan, Common Collective Trust [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[3]	1,066	751
Pension Plans [Member] | Defined Benefit Plan, Common Collective Trust [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[3]	0	0
Pension Plans [Member] | Defined Benefit Plan, Common Collective Trust [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[3]	1,066	751
Pension Plans [Member] | Defined Benefit Plan, Common Collective Trust [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[3]	$ 0	$ 0
Pension Plans [Member] | Common Collective Trusts - Equities [Member]
Employee Benefit Plans (Textual)
Defined benefit plan, actual plan asset allocations		80.00%	75.00%
Pension Plans [Member] | Common Collective Trusts - Bonds [Member]
Employee Benefit Plans (Textual)
Defined benefit plan, actual plan asset allocations		20.00%	25.00%
Pension Plans [Member] | Pooled Separate Accounts [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[4]	$ 316	$ 250
Pension Plans [Member] | Pooled Separate Accounts [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[4]	0	0
Pension Plans [Member] | Pooled Separate Accounts [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[4]	316	250
Pension Plans [Member] | Pooled Separate Accounts [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets	[4]	$ 0	$ 0
Pension Plans [Member] | Pooled Separate Accounts - Equities [Member]
Employee Benefit Plans (Textual)
Defined benefit plan, actual plan asset allocations		60.00%
Pension Plans [Member] | Pooled Separate Accounts - Bonds [Member]
Employee Benefit Plans (Textual)
Defined benefit plan, actual plan asset allocations		40.00%	40.00%
Pension Plans [Member] | Private Funds [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		$ 128	$ 104
Pension Plans [Member] | Private Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Private Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		128	104
Pension Plans [Member] | Private Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Insurance Contract [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		15	17
Pension Plans [Member] | Insurance Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Insurance Contract [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		15	17
Pension Plans [Member] | Insurance Contract [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Interest and Dividends Receivable [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		5	5
Pension Plans [Member] | Interest and Dividends Receivable [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		5	5
Pension Plans [Member] | Interest and Dividends Receivable [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Interest and Dividends Receivable [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Cash and Cash Equivalents [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		98	59
Pension Plans [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		98	59
Pension Plans [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Securities Transactions Payable, Net [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		(11)	(16)
Pension Plans [Member] | Securities Transactions Payable, Net [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		(11)	(16)
Pension Plans [Member] | Securities Transactions Payable, Net [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		0	0
Pension Plans [Member] | Securities Transactions Payable, Net [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Values of Qualified Pension Plan Assets
Fair value of qualified pension plan assets		$ 0	$ 0

[1] Plan assets include only the assets associated with pension plans subject to legal minimum funding standards. Plan assets associated with U.S. nonqualified pension plans are not included here because they are not protected from our creditors and therefore cannot be reflected as a reduction from our obligations under the pension plans. As a result, the reconciliation of funded status does not reflect the effect of plan assets that exist for all of our defined benefit plans. See Note 20 for the assets associated with certain U.S. nonqualified pension plans.

[2] This class of securities includes domestic and international stocks, which are held in a wide range of industry sectors.

[3] This class primarily includes investments in approximately 80 percent equities and 20 percent bonds as of December 31, 2020. As of December 31, 2019, this class included primarily investments in approximately 75 percent equities and 25 percent bonds.

[4] This class primarily includes investments in approximately 60 percent equities and 40 percent bonds as of December 31, 2020 and 2019. These pension assets are held by our international pension plans.