Business Combinations, Intangibles and Goodwill - Allocation of Purchase Price (Details) - Virtustream $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
Business Acquisition [Line Items]
Weighted-average useful life	9 years
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets	$ 18
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	14
Intangible assets	379
Business Acquisition, Goodwill, Expected Tax Deductible Amount	891
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	12
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	1,314
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities	(27)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent	(61)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other	(7)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	(95)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	$ 1,219
Purchased technology
Business Acquisition [Line Items]
Weighted-average useful life	8 years 7 months
Intangible assets	$ 302
Customer relationships and customer lists
Business Acquisition [Line Items]
Weighted-average useful life	12 years 3 months
Intangible assets	$ 50
Trademarks and tradenames
Business Acquisition [Line Items]
Weighted-average useful life	7 years 7 months
Intangible assets	$ 27