Significant accounting policies and practices - Narrative (Detail) - USD ($)
$ in Millions |
12 Months Ended |
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Dec. 31, 2018 |
Jan. 01, 2019 |
Jan. 01, 2018 |
Dec. 31, 2017 |
| Significant Accounting Policies [Line Items] |
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| Percentage of LIFO inventory |
39.00%
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| Excess of current or replacement costs over costs determined under LIFO |
$ 1,000
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| Minimum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Insurance interest rate assumption |
1.00%
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| Maximum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Insurance interest rate assumption |
7.00%
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| Insurance and Other [Member] |
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| Significant Accounting Policies [Line Items] |
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| Equipment held for lease |
$ 14,298
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$ 10,167
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| Aircraft repurchase liabilities and unearned lease revenues |
$ 4,593
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| Buildings and improvements [Member] | Minimum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
5 years
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| Buildings and improvements [Member] | Maximum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
50 years
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| Machinery and equipment [Member] | Minimum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
3 years
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| Machinery and equipment [Member] | Maximum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
25 years
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| Furniture, fixtures and other [Member] | Minimum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
3 years
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| Furniture, fixtures and other [Member] | Maximum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
15 years
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| Track structure and other roadway [Member] | Railroad [Member] | Minimum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
9 years
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| Track structure and other roadway [Member] | Railroad [Member] | Maximum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
100 years
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| Locomotives, freight cars and other equipment [Member] | Railroad [Member] | Minimum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
6 years
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| Locomotives, freight cars and other equipment [Member] | Railroad [Member] | Maximum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
41 years
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| Utility generation, transmission and distribution systems [Member] | Utilities and Energy [Member] | Minimum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
5 years
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| Utility generation, transmission and distribution systems [Member] | Utilities and Energy [Member] | Maximum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
80 years
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| Interstate natural gas pipeline assets [Member] | Utilities and Energy [Member] | Minimum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
3 years
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| Interstate natural gas pipeline assets [Member] | Utilities and Energy [Member] | Maximum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
80 years
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| Independent power plants and other assets [Member] | Utilities and Energy [Member] | Minimum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
3 years
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| Independent power plants and other assets [Member] | Utilities and Energy [Member] | Maximum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
30 years
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| Equipment held for lease [Member] | Minimum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
6 years
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| Equipment held for lease [Member] | Maximum [Member] |
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| Significant Accounting Policies [Line Items] |
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| Estimated useful life (in years) |
35 years
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| Other Assets [Member] |
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| Significant Accounting Policies [Line Items] |
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| Unamortized balances of deferred policy acquisition costs |
$ 2,658
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$ 2,529
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| Aircraft Sold Under Fractional Aircraft Ownership Programs [Member] | ASC 606 [Member] | Insurance and Other [Member] |
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| Significant Accounting Policies [Line Items] |
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| Equipment held for lease |
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$ 3,500
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| Aircraft repurchase liabilities and unearned lease revenues |
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$ 3,500
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| Subsequent Event [Member] | ASU 2016-02 [Member] |
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| Significant Accounting Policies [Line Items] |
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| Operating leases, right of use assets |
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$ 6,000
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| Operating lease liabilities |
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$ 6,000
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