Related Party Transactions (Related Party Transactions) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
All Services and Transactions Except Broker Dealer Activities [Member]
Related Party Transaction [Line Items]
Due from Related Parties	$ 5		$ 5		$ 2,839
Due to Related Parties	383		383		2,675
Revenue from Related Parties	11	$ 96	60	$ (110)
Related Party Transaction, Expenses from Transactions with Related Party	168	209	349	409
Broker Dealer Activities [Member]
Related Party Transaction [Line Items]
Due from Related Parties	18		18		$ 19
Revenue from Related Parties	55	56	111	110
Related Party Transaction, Expenses from Transactions with Related Party	$ 162	$ 194	$ 326	$ 320

For an unclassified balance sheet, amounts due from related parties including affiliates, employees, joint ventures, officers and stockholders, immediate families thereof, and pension funds.

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