Insurance (Rollforward of Unpaid Claims) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Balance at beginning of period	$ 18,159	$ 11,388
Less: Reinsurance recoverables	3,058	2,042
Net Balance, beginning of period	15,101	14,334
Incurred related to:
Current year	6,874	6,977
Prior years	(42)	(139)
Total incurred	6,832	6,838
Paid related to:
Current year	(3,777)	(3,710)
Prior years	(2,698)	(2,473)
Total paid	(6,475)	(6,183)
Net Balance, end of period	15,458
Add: Reinsurance recoverables	3,058	2,843
Balance at end of period (included in future policy benefits and other policy-related balances)	18,516	17,832
Scenario, Previously Reported
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Balance, beginning of period	15,101	9,346
Paid related to:
Net Balance, end of period		14,989
Cumulative adjustment
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Balance, beginning of period	$ 0	$ 4,988