Accrued Expenses and Other Liabilities (Schedule of Accrued Expenses and Other Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounts Payable and Accrued Liabilities [Abstract]
Accounts Payable	$ 390	$ 746
Accrued Employee Benefits	161	248
Liability for Claims and Claims Adjustment Expense	157	140	$ 175	$ 149
Derivative Liability, Fair Value, Gross Liability	56	41
Deferred Revenue	34	32
Cash collateral received from counterparties	31	17
Other Accrued Liabilities	626	556
Accounts Payable and Accrued Liabilities	$ 1,455	$ 1,780