Long-Term Debt and Credit Facilities - Principal and Carrying Amounts of Debt (Details) - USD ($)	Jun. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Principal	$ 1,594,000,000	$ 1,596,000,000
Carrying Value	1,305,000,000	1,303,000,000
AGUS [Member]
Debt Instrument [Line Items]
Principal	850,000,000	850,000,000
Carrying Value	847,000,000	847,000,000
AGMH [Member]
Debt Instrument [Line Items]
Principal	730,000,000	730,000,000
Carrying Value	442,000,000	437,000,000
AGM [Member]
Debt Instrument [Line Items]
Principal	14,000,000	16,000,000
Carrying Value	$ 16,000,000	$ 19,000,000
Senior Notes [Member] \| AGUS [Member] \| Senior Notes 7.0 Percent [Member]
Debt Instrument [Line Items]
Interest rate of debt (as a percent)	7.00%	7.00%
Principal	$ 200,000,000	$ 200,000,000
Carrying Value	$ 198,000,000	$ 198,000,000
Senior Notes [Member] \| AGUS [Member] \| Senior Notes 5.0 Percent [Member]
Debt Instrument [Line Items]
Interest rate of debt (as a percent)	5.00%	5.00%
Principal	$ 500,000,000	$ 500,000,000
Carrying Value	499,000,000	499,000,000
Enhanced Junior Subordinated Debentures [Member] \| AGUS [Member]
Debt Instrument [Line Items]
Principal	150,000,000	150,000,000
Carrying Value	$ 150,000,000	$ 150,000,000
Corporate securities [Member] \| AGMH [Member] \| QUIBS 6.875 Percent [Member]
Debt Instrument [Line Items]
Interest rate of debt (as a percent)	6.875%	6.875%
Principal	$ 100,000,000	$ 100,000,000
Carrying Value	$ 69,000,000	$ 68,000,000
Notes Payable, Other Payables [Member] \| AGMH [Member] \| 6.25% Notes [Member]
Debt Instrument [Line Items]
Interest rate of debt (as a percent)	6.25%	6.25%
Principal	$ 230,000,000	$ 230,000,000
Carrying Value	$ 140,000,000	$ 139,000,000
Notes Payable, Other Payables [Member] \| AGMH [Member] \| Notes Payable 5.60 Percent [Member]
Debt Instrument [Line Items]
Interest rate of debt (as a percent)	5.60%	5.60%
Principal	$ 100,000,000	$ 100,000,000
Carrying Value	55,000,000	55,000,000
Notes Payable, Other Payables [Member] \| AGM [Member]
Debt Instrument [Line Items]
Principal	14,000,000	16,000,000
Carrying Value	16,000,000	19,000,000
Junior Subordinated Debt [Member] \| AGMH [Member]
Debt Instrument [Line Items]
Principal	300,000,000	300,000,000
Carrying Value	$ 178,000,000	$ 175,000,000

Face (par) amount of debt instrument at time of issuance.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

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Contractual interest rate for funds borrowed, under the debt agreement.

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-Name Accounting Standards Codification

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No definition available.

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- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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

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