Income Taxes - A Reconciliation of Beginning and Ending Amounts of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 461	$ 241	$ 239
Additions on tax position related to the current year	1	186	2
Additions for tax positions of prior years	18	41	6
Additions for tax positions taken in conjunction with acquisition of Tim Hortons	0	2	0
Reductions for tax positions of prior year	(18)	0	(1)
Reductions for settlement	(18)	(2)	(5)
Reductions due to statute expiration	(3)	(7)	0
Ending balance	$ 441	$ 461	$ 241