Benefit Plans - Additional Information (Details)		3 Months Ended	12 Months Ended
	Jul. 11, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2018 arrangement
Defined Benefit Plan Disclosure [Line Items]
Pension plans resulted in net pension liability			$ 709,000,000	$ 1,114,000,000
Plan assets related to certain insurance contracts			67,000,000	67,000,000
Expense for defined contribution plans			72,000,000	57,000,000	$ 43,000,000
Multiemployer Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Multiemployer pension plans contributions			$ 5,000,000	17,000,000	26,000,000
Multiemployer Pension Plans | Bakery and Confectionery Union and Industry International Pension Fund
Defined Benefit Plan Disclosure [Line Items]
Multiemployer pension plans contributions				12,000,000	22,000,000
Multiemployer Pension Plans | Bakery and Confectionery Union and Industry International Pension Fund
Defined Benefit Plan Disclosure [Line Items]
Pension fund			Bakery and Confectionery Union and Industry International Pension Fund
Multiemployer Pension Plans | Multiemployer Plan, Individually Insignificant Multiemployer Plans
Defined Benefit Plan Disclosure [Line Items]
Multiemployer pension plans contributions			$ 5,000,000	5,000,000	4,000,000
Multiemployer Plans, Postretirement Benefit | Multiemployer Medical Plans
Defined Benefit Plan Disclosure [Line Items]
Multiemployer pension plans contributions			$ 20,000,000	19,000,000	$ 18,000,000
U.S. And International Investment Grade Debt Securities | Fixed-income securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage			95.00%
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Period for recognition of net periodic benefit costs			4 years
U.S. Plans | Bakery, Confectionery, Tobacco and Grain Millers Union (“BCTGM”) | Multiemployer Pension Plans | Bakery and Confectionery Union and Industry International Pension Fund
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plan, number of expired collective-bargaining arrangements | arrangement						8
U.S. Plans | North America | Bakery, Confectionery, Tobacco and Grain Millers Union (“BCTGM”) | Multiemployer Pension Plans | Bakery and Confectionery Union and Industry International Pension Fund
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plan, withdrawal obligation	$ 526,000,000		$ 391,000,000	429,000,000
Multiemployer plan, withdrawal obligation term	20 years
U.S. Plans | Selling, general and administrative expenses | North America | Bakery, Confectionery, Tobacco and Grain Millers Union (“BCTGM”) | Multiemployer Pension Plans | Bakery and Confectionery Union and Industry International Pension Fund
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plan, final adjustment to reduce withdrawal liability		$ 35,000,000
U.S. Plans | Other current liabilities | North America | Bakery, Confectionery, Tobacco and Grain Millers Union (“BCTGM”) | Multiemployer Pension Plans | Bakery and Confectionery Union and Industry International Pension Fund
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plan, withdrawal obligation			14,000,000
U.S. Plans | Other liabilities | North America | Bakery, Confectionery, Tobacco and Grain Millers Union (“BCTGM”) | Multiemployer Pension Plans | Bakery and Confectionery Union and Industry International Pension Fund
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plan, withdrawal obligation			377,000,000
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Pension plans resulted in net pension liability			709,000,000	1,114,000,000
Estimated loss from experience differences			133,000,000
Estimated prior service credit			6,000,000
Pension Plans | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation			1,741,000,000	$ 1,488,000,000
Employer contribution			8,000,000
Estimated future employer contributions			$ 16,000,000
Weighted-average discount rate			3.44%	4.40%
Rate of compensation increase			4.00%	4.00%
Pension Plans | Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation			$ 10,236,000,000	$ 9,374,000,000
Employer contribution			248,000,000
Employees contribution			13,000,000
Estimated future employer contributions			$ 230,000,000
Weighted-average discount rate			1.74%	2.45%
Rate of compensation increase			3.17%	3.31%
Pension Plans | Non-U.S. Plans | Fixed-income securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage			57.00%
Pension Plans | Non-U.S. Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage			25.00%
Pension Plans | Non-U.S. Plans | Buy-in annuity policies
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage			12.00%
Pension Plans | Non-U.S. Plans | Real estate
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage			6.00%
Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Current portion of our accrued postretirement benefit obligation			$ 16,000,000	$ 15,000,000
Postretirement Benefit Plans | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Weighted-average discount rate			3.41%	4.37%
Postretirement Benefit Plans | Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Weighted-average discount rate			3.86%	4.40%
Postretirement Health Care Plan
Defined Benefit Plan Disclosure [Line Items]
Estimated loss from experience differences			$ 10,000,000
Estimated prior service credit			$ 30,000,000
Postemployment Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Weighted-average discount rate			5.30%	6.70%
Ultimate annual turnover rate			0.30%	0.30%
Rate of compensation increase			4.00%	4.00%
Defined benefit plan, amount to be amortized from accumulated other comprehensive income (loss) next fiscal year			$ 4,000,000