Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions		Jul. 01, 2019	Jan. 01, 2019	Jul. 01, 2018	Jan. 01, 2018
Retained Earnings
Accounting Standards Adopted
Cumulative catch-up adjustment to equity component	[1]	$ 0	$ 63	$ 0	$ 306
Accounting Standards Update 2018-11 | Other Assets
Accounting Standards Adopted
Effect of adopting the new accounting standard on balance sheet			(4,000)
Accounting Standards Update 2018-11 | Other Liabilities and Accrued Expenses
Accounting Standards Adopted
Effect of adopting the new accounting standard on balance sheet			4,000
Accounting Standards Update 2018-11 | Retained Earnings
Accounting Standards Adopted
Cumulative catch-up adjustment to equity component			$ 63

[1] Cumulative adjustments for accounting changes relate to the adoption of certain accounting updates during the current and prior year periods. See Notes 2 and 14 for further information.