Stockholders' equity (Accumulated Other Comprehensive Income (Loss), Textual) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Income tax expense or (benefit) for reclassification adjustments to income for available-for-sale securities	$ 7	$ 14	$ (3)
Income taxes expense or (benefit) for unrealized gains and losses for available-for-sale securities	(1)	(22)	9
Income taxes expense or (benefit) for unrealized gains and losses for cash flow hedges	14	(28)	(21)
Income tax expense or (benefit) reclassification adjustments to income for cash flow hedges	$ 110	$ 46	$ (55)