Summary of Significant Accounting Policies - Schedule of Cash and Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 8,080	$ 6,268	$ 2,198	$ 3,686
Restricted cash included in prepaid expenses and other current assets	193	246	131	193
Restricted cash included in other non-current assets	274	269	354	398
Total as presented in the consolidated statements of cash flows	$ 8,547	$ 6,783	$ 2,683	$ 4,277