Summary of Investments - SOI Ltd partnership Sec lending Special deposits (Details 5) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Limited partnership and other corporation interests	$ 47,481	$ 49,421
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	6,308	7,464
Maximum exposure to loss in relation to the activities of the VIEs	6,308	7,464
Special deposits and securities lending
Fair value of securities on deposit with governmental authorities	14,785	14,612
Securities loaned to third parties at amortized cost	169,739us-gaap_SecuritiesLoaned	15,252us-gaap_SecuritiesLoaned
Estimated fair value of securities loaned to third parties	170,659gac_SecuritiesLoanedFairValue	15,423gac_SecuritiesLoanedFairValue
Restricted cash received as collateral	89,906	13,741
Securities received as collateral	$ 85,137	$ 2,131

Fair value of securities loaned to other entities.

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

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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).

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-Publisher FASB

-Name Accounting Standards Codification

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-Section 50

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

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-Name Regulation S-X (SX)

-Number 210

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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.

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

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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 and not elected to be offset.

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

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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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