Borrowings - Long-Term Debt, Components (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Borrowings
Long-term debt, gross	$ 42,792	$ 41,145
Less: net unamortized discount	838	839
Less: net unamortized debt issuance cost	84	82
Add: fair value adjustment	627	669
Long-term debt (including current maturities)	42,498	40,893
Less: current maturities	8,055	6,239
Long-term debt (excluding current portion)	34,441	34,655
IBM International Group Capital, LLC
Borrowings
Long-term debt, gross	$ 0
Ownership interest in subsidiary (as a percent)	100.00%
U.S. dollars
Borrowings
Long-term debt, gross	$ 32,309	30,563
Euros
Borrowings
Long-term debt, gross	$ 7,217	7,122
Debt instrument, average interest rate percentage (as a percent)	1.60%
Pound sterling
Borrowings
Long-term debt, gross	$ 1,312	1,296
Debt instrument, average interest rate percentage (as a percent)	2.70%
Japanese yen
Borrowings
Long-term debt, gross	$ 1,649	1,576
Debt instrument, average interest rate percentage (as a percent)	0.90%
Canadian
Borrowings
Long-term debt, gross		$ 373
Debt instrument, average interest rate percentage (as a percent)		2.20%
Other
Borrowings
Long-term debt, gross	$ 305	$ 215
Debt instrument, average interest rate percentage (as a percent)	10.00%
Maturing 2017 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 3,980	5,104
Debt instrument, average interest rate percentage (as a percent)	4.69%
Maturing 2018 Through 2019 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 8,967	8,856
Debt instrument, average interest rate percentage (as a percent)	3.24%
Maturing 2020 Through 2021 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 6,198	4,941
Debt instrument, average interest rate percentage (as a percent)	1.86%
Maturing 2022 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 2,903	1,901
Debt instrument, average interest rate percentage (as a percent)	1.54%
Maturing 2023 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 1,500	1,500
Debt instrument, average interest rate percentage (as a percent)	3.38%
Maturing 2024 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 2,000	2,000
Debt instrument, average interest rate percentage (as a percent)	3.63%
Maturing 2025 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 600	600
Debt instrument, average interest rate percentage (as a percent)	7.00%
Maturing 2026 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 1,350	1,350
Debt instrument, average interest rate percentage (as a percent)	3.45%
Maturing 2027 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 969	469
Debt instrument, average interest rate percentage (as a percent)	3.01%
Maturing 2028 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 313	313
Debt instrument, average interest rate percentage (as a percent)	6.50%
Maturing 2032 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 600	600
Debt instrument, average interest rate percentage (as a percent)	5.88%
Maturing 2038 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 83	83
Debt instrument, average interest rate percentage (as a percent)	8.00%
Maturing 2039 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 745	745
Debt instrument, average interest rate percentage (as a percent)	5.60%
Maturing 2042 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 1,107	1,107
Debt instrument, average interest rate percentage (as a percent)	4.00%
Maturing 2045 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 27	27
Debt instrument, average interest rate percentage (as a percent)	7.00%
Maturing 2046 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 650	650
Debt instrument, average interest rate percentage (as a percent)	4.70%
Maturing 2096 \| U.S. dollars
Borrowings
Long-term debt, gross	$ 316	$ 316
Debt instrument, average interest rate percentage (as a percent)	7.13%

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-SubTopic 30
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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, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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