Income taxes (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax assets:
NOL and credit carryforwards	$ 810	$ 812
Accrued expenses	428	362
Expenses capitalized for tax	185	155
Stock-based compensation	95	99
Other	174	154
Total deferred income tax assets	1,692	1,582
Valuation allowance	(509)	(497)
Net deferred income tax assets	1,183	1,085
Deferred income tax liabilities:
Acquired intangible assets	(1,509)	(1,748)
Debt	(184)	(184)
Other	(267)	(240)
Total deferred income tax liabilities	(1,960)	(2,172)
Total deferred income taxes, net	$ (777)	$ (1,087)

The tax effect as of the balance sheet date of the amount of the estimated future tax deductions arising from acquired net operating loss and credit carryforwards and which can only be realized if sufficient tax-basis income is generated in future periods to enable the deduction to be taken.

No definition available.