Insurance (Rollforward of Unpaid Claims) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Balance, beginning of period	$ 17,094	$ 16,157
Less: Reinsurance Recoverables	2,198	1,968
Net balance, beginning of period	14,896	14,189
Incurred related to:
Current period	6,504	6,637
Prior periods (2)	(148)	(127)
Total incurred	6,356	6,510
Paid related to:
Current period	(3,339)	(3,723)
Prior periods	(2,719)	(2,604)
Total paid	(6,058)	(6,327)
Net balance, end of period	15,194	14,372
Add: Reinsurance Recoverables	2,237	2,123
Balance, end of period (included in future policy benefits and other policy-related balances)	$ 17,431	16,495
Restatement Adjustment
Paid related to:
Net balance, end of period		(131)
Add: Reinsurance Recoverables		$ 144