Income taxes (Provision for Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current provision:
Federal	$ 1,284	$ 1,270	$ 8,615
State	39	17	5
Foreign	277	227	275
Total current provision	1,600	1,514	8,895
Deferred (benefit) provision:
Federal	(276)	(317)	(1,120)
State	(22)	(7)	0
Foreign	(6)	(39)	(157)
Total deferred (benefit) provision	(304)	(363)	(1,277)
Total provision for income taxes	$ 1,296	$ 1,151	$ 7,618