Acquisitions and Divestitures - Components of Assets and Liabilities, and Operating Loss, of Businesses Held for Sale (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Operating Loss of Business Disposed of
Operating loss	$ 0	$ (5)	$ 0	$ (12)
Quant House SAS | Disposal Group, Held-for-sale, Not Discontinued Operations
Assets and Liabilities of Business Held for Sale
Accounts receivable, net					$ 4
Other assets					3
Assets of a business held for sale					7
Accounts payable and accrued expenses					3
Unearned revenue					7
Other liabilities					35
Liabilities of a business held for sale					$ 45