Closed Block (Liabilities and Assets) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Closed Block Liabilities
Future policy benefits	$ 42,105	$ 42,586
Other policy-related balances	301	298
Policyholder dividends payable	507	466
Policyholder dividend obligation	2,013	3,828	2,919
Other liabilities	724	602
Total closed block liabilities	45,650	47,780
Assets Designated to the Closed Block
Fixed maturity securities available-for-sale, at estimated fair value	28,124	30,546
Equity securities available-for-sale, at estimated fair value	87	41
Mortgage loans	6,520	6,192
Policy loans	4,669	4,670
Real estate and real estate joint ventures	481	459
Other invested assets	923	953
Total investments	40,804	42,861
Cash and cash equivalents	404	381
Accrued investment income	497	481
Premiums, reinsurance and other receivables	101	107
Current income tax recoverable	15	2
Deferred income tax assets	292	319
Total assets designated to the closed block	42,113	44,151
Excess of closed block liabilities over assets designated to the closed block	3,537	3,629
Amounts included in AOCI:
Unrealized investment gains (losses), net of income tax	1,682	2,891
Unrealized gains (losses) on derivatives, net of income tax	2	9
Allocated to policyholder dividend obligation, net of income tax	(1,309)	(2,488)
Total amounts included in AOCI	375	412
Maximum future earnings to be recognized from closed block assets and liabilities	$ 3,912	$ 4,041