Notes Payable, Long-Term Debt and Available Credit Facilities (Committed and Available Credit Facilities) (Details) - Successor $ in Millions	Sep. 30, 2017 USD ($)
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 8,800
Line of Credit Facility, Remaining Borrowing Capacity	6,445
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	3,000
Line of Credit Facility, Remaining Borrowing Capacity	2,945
Term Loan Facility due 2019 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	4,500
Line of Credit Facility, Remaining Borrowing Capacity	3,500
Repurchase Facility [Member] | Securities Sold under Agreements to Repurchase [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,300
Line of Credit Facility, Remaining Borrowing Capacity	$ 0