SOI Limited partnerships Sec Lending Special Deposits (Details 5) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Limited partnership and other corporation interests	$ 49,421	$ 79,236
Interest in various upper-tier LIHLPs (as a percent)	99.00%
Nature and activities of the VIEs and the effect on financial statements
Carrying value in relation to the activities of the VIEs	7,464	31,563
Maximum exposure to loss in relation to the activities of the VIEs	7,464	31,563
Special deposits and securities lending
Fair value of securities on deposit with governmental authorities	14,612	14,072
Securities loaned to third parties at amortized cost	15,252us-gaap_SecuritiesLoaned	28,178us-gaap_SecuritiesLoaned
Estimated fair value of securities loaned to third parties	15,423gac_SecuritiesLoanedFairValue	27,166gac_SecuritiesLoanedFairValue
Restricted cash received as collateral	13,741	18,534
Securities received as collateral	$ 2,131	$ 9,424

Fair value of securities loaned to other entities.

No definition available.

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- Definition

The amount of securities received as collateral in return for loaning securities to another party.

+ References

No definition available.

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- Definition

Amount of cash subject to withdrawal restrictions, restricted deposits held as compensating balances, and cash and securities segregated in compliance with regulations (such as cash deposited in a special reserve account for the exclusive benefit of customers).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 305

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6478312&loc=d3e61473-112792

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- Definition

The amount of cash received as security in return for loaning securities to another party.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

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-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

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- Definition

Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

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- Definition

The number of units or percentage investment held by one or more members or limited partners of the LLC or LP.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 272

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

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- Definition

Amount, after the effects of master netting arrangements, of securities loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (c)

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-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 10

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-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (b)

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-Name Accounting Standards Codification

-Topic 940

-SubTopic 405

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- Definition

The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 3

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The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

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