Subsequent Events (Reinsurance Subsequent Events) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 01, 2017
Subsequent Event [Line Items]
Liability for Future Policy Benefits		$ 31,684	$ 29,894
Policyholder account balances		35,587	35,661	$ 35,486
Other Liabilities		10,147	7,682
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		(4,708)	1,054	$ 290
Ceded Reinsurance [Member]
Subsequent Event [Line Items]
Liability for Future Policy Benefits		(117)	(70)
Policyholder account balances		0	0
Other Liabilities		5,669	5,030
Ceded Reinsurance [Member] | Affiliated Entity [Member]
Subsequent Event [Line Items]
Liability for Future Policy Benefits		(117)	(70)
Policyholder account balances		0	0
Other Liabilities		$ 5,344	$ 4,691
Ceded Reinsurance [Member] | Subsequent Event [Member] | Affiliated Entity [Member] | Affiliate Recapture Variable Annuities [Member]
Subsequent Event [Line Items]
Cash, Cash Equivalents, and Short-term Investments					$ 34
Liability for Future Policy Benefits					79
Policyholder account balances					387
Other Liabilities					427
Ceded Reinsurance [Member] | Subsequent Event [Member] | Affiliated Entity [Member] | MLUS Recapture GMIB [Member]
Subsequent Event [Line Items]
Cash, Cash Equivalents, and Short-term Investments					568
Liability for Future Policy Benefits					106
Policyholder account balances					$ 460
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ 2