Debt - Repayments of Principal and Interest (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term Debt	$ 73,876	$ 54,346
Interest payments in 2017	1,624
Interest payments in 2018	1,204
Interest payments in 2019	799
Interest payments in 2020	573
Interest payments in 2021	376
Interest payments thereafter	793
Interest payments	5,369
Total repayments in 2017	30,220
Total repayments in 2018	16,944
Total repayments in 2019	12,030
Total repayments in 2020	6,487
Total repayments in 2021	5,474
Total repayments thereafter	8,584
Total repayments of principal and interest	79,739
Secured Debt [Member]
Debt Instrument [Line Items]
Repayments of principal in 2017	21,268
Repayments of principal in 2018	11,573
Repayments of principal in 2019	4,880
Repayments of principal in 2020	1,264
Repayments of principal in 2021	348
Repayments of principal thereafter	0
Long-term Debt	39,333
Unsecured Debt [Member]
Debt Instrument [Line Items]
Repayments of principal in 2017	7,328
Repayments of principal in 2018	4,167
Repayments of principal in 2019	6,351
Repayments of principal in 2020	4,650
Repayments of principal in 2021	4,750
Repayments of principal thereafter	7,791
Long-term Debt	$ 35,037

Amount of interest payments scheduled after the fifth fiscal year following the latest fiscal year.

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Amount of interest payments scheduled in the next fiscal year following the latest fiscal year.

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Amount of interest payments scheduled in the fifth fiscal year following the latest fiscal year.

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Amount of interest payments scheduled in the fourth fiscal year following the latest fiscal year.

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Amount of interest payments scheduled in the third fiscal year following the latest fiscal year.

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Amount of interest payments scheduled in the second fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled after the fifth fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled in the next fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled in the fifth fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled in the fourth fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled in the third fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled in the second fiscal year following the latest fiscal year.

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Repayments of Principal and Interest

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of interest payable on debt, including, but not limited to, trade payables.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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