Income taxes (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred income tax assets:
NOL and credit carryforwards	$ 794	$ 800
Accrued expenses	561	457
Expenses capitalized for tax	144	170
Stock-based compensation	92	91
Other	301	269
Total deferred income tax assets	1,892	1,787
Valuation allowance	(571)	(517)
Net deferred income tax assets	1,321	1,270
Deferred income tax liabilities:
Acquired intangible assets	(903)	(1,288)
Debt	(282)	(210)
Deferred Tax Liabilities, Property, Plant and Equipment	(148)	(53)
Other	(189)	(233)
Total deferred income tax liabilities	(1,522)	(1,784)
Total deferred income taxes, net	$ (201)	$ (514)