Income Taxes - Components of Our Net Deferred Tax Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets
State	$ 34	$ 18
Foreign	630	559
Tax credits	276	179
Postretirement benefits other than pensions	19	20
Pensions	148	158
Payroll accruals	31	23
Book over tax depreciation	244	91
Research expense capitalized for tax	102	72
Other accruals	216	225
Valuation allowance	(1,428)	(762)
Total deferred tax assets	272	583
Deferred tax liabilities
Amortization of intangibles	11	24
Other	65	58
Total deferred tax liabilities	76	82
Net deferred tax assets	$ 196	$ 501

Deferred Tax Assets, Book Over Tax Depreciation

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from in-process research and development costs expensed in connection with a business combination.

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