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Related Party Transactions (Narratives) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jul. 31, 2017
Related Party Transaction
Asset impairments		$ 95,000,000	$ 0	$ 0
Dividends paid		$ 421,000,000	385,000,000	341,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations \| Brazilian Venture
Related Party Transaction
Asset impairments	$ 95,000,000
Cardinal Holdings
Related Party Transaction
Ownership percentage (percent)					40.00%
Banco Bradesco \| Joint venture
Related Party Transaction
Ownership percentage (percent)		51.00%
Capco Consulting Business \| Cardinal Holdings \| Joint venture
Related Party Transaction
Ownership percentage (percent)					60.00%
Banco Bradesco \| Joint venture
Related Party Transaction
Dividends paid		$ 26,000,000	23,000,000
Noncontrolling interest value		0
Total related party revenues		332,000,000	329,000,000	$ 272,000,000
Banco Bradesco \| Joint venture \| Favorable (unfavorable) Currency Impact
Related Party Transaction
Total related party revenues		$ (46,000,000)	$ 24,000,000
Banco Bradesco \| Brazilian Venture
Related Party Transaction
Ownership percentage (percent)		100.00%