Cash and Securities Segregated Under Federal Regulations and Other Requirements (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash and Securities Segregated Under Federal Regulations and Other Requirements [Abstract]
United States Treasury Bills in special reserve bank custody account for exclusive benefit of brokerage customers of SCB LLC	$ 800,000,000	$ 1,500,000,000	$ 1,200,000,000
Restricted funds held for benefit of customers by AllianceBernstein Investments, Inc.	$ 39,900,000	$ 42,200,000	$ 39,900,000

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_RestrictedCashAndCashEquivalents
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant