Accrued Expenses - Summary of Other Accrued Expenses (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Professional liability risks	$ 466	$ 429
Defined contribution benefit plan	459	67
Interest	429	406
Taxes other than income	308	299
Other	962	782
Other accrued expenses	$ 2,624	$ 1,983