Income Taxes - Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Loss carryforwards U.S. - Federal/States	$ 211	$ 198
Loss carryforwards - Foreign	2,149	1,062
Accrued liabilities, reserves, & other expenses	901	968
Stock-based compensation	1,026	1,073
Deferred revenue	349	330
Assets held for investment	35	66
Depreciation & amortization	279	179
Other items	167	171
Tax credits	381	39
Total gross deferred tax assets	5,498	4,086
Less valuation allowance	(2,538)	(1,012)
Deferred tax assets, net of valuation allowance	2,960	3,074
Deferred tax liabilities:
Depreciation & amortization	(2,568)	(2,332)
Acquisition related intangible assets	(531)	(226)
Other items	(58)	(62)
Net deferred tax assets, net of valuation allowance		454
Net deferred tax liabilities, net of valuation allowance	$ (197)
Excess Stock-Based Compensation Carryforward
Deferred tax assets:
Loss carryforwards U.S. - Federal/States		18
Loss carryforwards - Foreign		9
Tax credits		$ 659