Debt and Borrowing Arrangements - Additional Information (Details) SFr in Millions | May 07, 2018USD ($) | Apr. 17, 2018USD ($) | Apr. 02, 2018USD ($) | Mar. 02, 2018USD ($) | Mar. 02, 2018CAD ($) | Feb. 28, 2018USD ($) | Feb. 01, 2018USD ($) | Jan. 26, 2018USD ($) | Jan. 26, 2018CHF (SFr) | Oct. 13, 2016 | Jun. 30, 2018USD ($) | Jun. 30, 2017USD ($) | Jun. 30, 2018USD ($) | Jun. 30, 2017USD ($) | Sep. 30, 2017 | May 03, 2018USD ($) | Mar. 02, 2018CAD ($) | Dec. 31, 2017USD ($) | Dec. 31, 2016 |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Proceeds from issuance of debt | | | | | | | | | | | | | $ 2,948,000,000 | $ 350,000,000 | | | | | |
Loss on debt extinguishment | | | | | | | | | | | $ 140,000,000 | $ 11,000,000 | 140,000,000 | 11,000,000 | | | | | |
Long-term debt repaid | | | | | | | | | | | | | $ 1,442,000,000 | $ 1,469,000,000 | | | | | |
Weighted-average interest rate | | | | | | | | | | | 2.40% | | 2.40% | | | | | 2.10% | 2.20% |
Fair value of total debt | | | | | | | | | | | $ 20,089,000,000 | | $ 20,089,000,000 | | | | | $ 18,354,000,000 | |
Carrying value of total debt | | | | | | | | | | | 19,711,000,000 | | 19,711,000,000 | | | | | 17,652,000,000 | |
Notes Payable | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, principal amount | | | | | | | | | | | | | | | | $ 2,500,000,000 | | | |
Proceeds from issuance of debt | $ 2,480,000,000 | | | | | | | | | | | | | | | | | | |
Debt issuance costs | | | | | | | | | | | | | | | | 22,000,000 | | | |
Debt repurchased amount | | $ 570,000,000 | | | | | | | | | | | | | | | | | |
Notes Payable | 3.000% U.S. dollar-denominated Fixed-rate Notes Due May 2020 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, principal amount | | | | | | | | | | | | | | | | $ 750,000,000 | | | |
Debt instrument, interest rate | | | | | | | | | | | | | | | | 3.00% | | | |
Notes Payable | 3.625% U.S. dollar-denominated Fixed-rate Notes Due May 2023 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, principal amount | | | | | | | | | | | | | | | | $ 750,000,000 | | | |
Debt instrument, interest rate | | | | | | | | | | | | | | | | 3.625% | | | |
Notes Payable | 4.125% U.S. dollar-denominated Fixed-rate Notes Due May 2028 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, principal amount | | | | | | | | | | | | | | | | $ 700,000,000 | | | |
Debt instrument, interest rate | | | | | | | | | | | | | | | | 4.125% | | | |
Notes Payable | 4.625% U.S. dollar-denominated Fixed-rate Notes Due May 2048 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, principal amount | | | | | | | | | | | | | | | | $ 300,000,000 | | | |
Debt instrument, interest rate | | | | | | | | | | | | | | | | 4.625% | | | |
Notes Payable | 6.500% U.S. dollar-denominated Notes Due February 2040 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, interest rate | | 6.50% | | | | | | | | | | | | | | | | | |
Debt repurchased amount | | $ 241,000,000 | | | | | | | | | | | | | | | | | |
Notes Payable | 5.375% U.S. dollar-denominated Notes Due February 2020 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, interest rate | | 5.375% | | | | | | | | | | | | | | | | | |
Debt repurchased amount | | $ 97,600,000 | | | | | | | | | | | | | | | | | |
Notes Payable | 6.500% U.S. dollar-denominated Notes Due November 2031 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, interest rate | | 6.50% | | | | | | | | | | | | | | | | | |
Debt repurchased amount | | $ 75,800,000 | | | | | | | | | | | | | | | | | |
Notes Payable | 6.875% U.S. dollar-denominated Notes Due February 2038 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, interest rate | | 6.875% | | | | | | | | | | | | | | | | | |
Debt repurchased amount | | $ 72,100,000 | | | | | | | | | | | | | | | | | |
Notes Payable | 6.125% U.S. dollar-denominated Notes Due August 2018 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, interest rate | | 6.125% | | | | | | | | | | | | | | | | | |
Debt repurchased amount | | $ 42,600,000 | | | | | | | | | | | | | | | | | |
Notes Payable | 6.875% U.S. dollar-denominated Notes Due January 2039 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, interest rate | | 6.875% | | | | | | | | | | | | | | | | | |
Debt repurchased amount | | $ 29,300,000 | | | | | | | | | | | | | | | | | |
Notes Payable | 7.000% U.S. dollar-denominated Notes Due August 2037 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, interest rate | | 7.00% | | | | | | | | | | | | | | | | | |
Debt repurchased amount | | $ 11,700,000 | | | | | | | | | | | | | | | | | |
Notes Payable | 3.250% Canadian dollar-denominated Notes Due March 2025 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, principal amount | | | | | | | | | | | | | | | | | $ 600,000,000 | | |
Debt instrument, interest rate | | | | 3.25% | | | | | | | | | | | | | 3.25% | | |
Debt issuance costs | | | | $ 4,000,000 | | | | | | | | | | | | | | | |
Proceeds from issuance of debt, net of discounts and underwriting fees | | | | $ 461,000,000 | $ 595,000,000 | | | | | | | | | | | | | | |
Notes Payable | 6.125% U.S. dollar-denominated Notes | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, interest rate | | | | | | | 6.125% | | | | | | | | | | | | |
Long-term debt repaid | | | | | | | $ 478,000,000 | | | | | | | | | | | | |
Notes Payable | 0.080% Swiss franc-denominated Notes | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Debt instrument, interest rate | | | | | | | | 0.08% | 0.08% | | | | | | | | | | |
Long-term debt repaid | | | | | | | | $ 260,000,000 | SFr 250 | | | | | | | | | | |
Revolving Credit Facility | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Revolving credit facility, maximum borrowing capacity | | | | | | $ 1,500,000,000 | | | | | | | | | | | | | |
Line of credit facility outstanding amount | | | | | | | | | | | 0 | | 0 | | | | | | |
Line of credit, expiration period | | | | | | 364 days | | | | | | | | | | | | | |
Revolving credit facility expiration date | | | | | | Feb. 27, 2019 | | | | | | | | | | | | | |
Revolving Credit Facility, October 11, 2021 | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Revolving credit facility, maximum borrowing capacity | | | | | | $ 4,500,000,000 | | | | | 4,500,000,000 | | 4,500,000,000 | | | | | | |
Line of credit facility outstanding amount | | | | | | | | | | | 0 | | 0 | | | | | | |
Revolving credit facility expiration date | | | | | | | | | | Oct. 11, 2018 | | | | | Oct. 11, 2021 | | | | |
Revolving credit facility debt covenant | | | | | | | | | | | | | 24,600,000,000 | | | | | | |
Total shareholders' equity, excluding accumulated other comprehensive earnings / (losses) | | | | | | | | | | | 35,700,000,000 | | 35,700,000,000 | | | | | | |
International Subsidiaries | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Revolving credit facility, maximum borrowing capacity | | | | | | | | | | | $ 1,800,000,000 | | $ 1,800,000,000 | | | | | $ 2,000,000,000 | |
Commercial paper | Minimum | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Commercial paper, maturity period | | | | | | | | | | | | | 2 days | | | | | | |
Commercial paper | Maximum | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Commercial paper, maturity period | | | | | | | | | | | | | 172 days | | | | | | |
Bank loans | Revolving Credit Facility | 364-Day Senior Unsecured Credit Facility | | | | | | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | | | | | | |
Revolving credit facility, maximum borrowing capacity | | | $ 2,000,000,000 | | | | | | | | | | | | | | | | |
Borrowings from line of credit facility | | $ 714,000,000 | | | | | | | | | | | | | | | | | |
Repayments of lines of credit | $ 714,000,000 | | | | | | | | | | | | | | | | | | |
Line of credit, expiration period | | | 364 days | | | | | | | | | | | | | | | | |
Loss on debt extinguishment | | | | | | | | | | | | | $ 140,000,000 | | | | | | |