Commitments and Contingencies	9 Months Ended
Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings Lawsuits arise in the ordinary course of the Company’s business. It is the opinion of the Company’s management, based upon the information available, that the expected outcome of litigation against the Company, individually or in the aggregate, will not have a material adverse effect on the Company’s financial position or liquidity, although an adverse resolution of litigation against the Company in a fiscal quarter or year could have a material adverse effect on the Company’s results of operations in a particular quarter or year. In addition, in the ordinary course of their respective businesses, certain of AGL's subsidiaries assert claims in legal proceedings against third parties to recover losses paid in prior periods or prevent losses in the future. For example, the Company has commenced a number of legal actions in the Federal District Court for Puerto Rico to enforce its rights with respect to the obligations it insures of Puerto Rico and various of its related authorities and public corporations. See "Exposure to Puerto Rico" section of Note 4, Outstanding Exposure, for a description of such actions. See "Recovery Litigation" section of Note 5, Expected Loss to be Paid, for a description of recovery litigation unrelated to Puerto Rico. The amounts, if any, the Company will recover in these and other proceedings to recover losses are uncertain, and recoveries, or failure to obtain recoveries, in any one or more of these proceedings during any quarter or year could be material to the Company's results of operations in that particular quarter or year. The Company also receives subpoenas duces tecum and interrogatories from regulators from time to time. Litigation On November 28, 2011, Lehman Brothers International (Europe) (in administration) (LBIE) sued AG Financial Products Inc. (AGFP), an affiliate of AGC which in the past had provided credit protection to counterparties under CDS. AGC acts as the credit support provider of AGFP under these CDS. LBIE’s complaint, which was filed in the Supreme Court of the State of New York, asserted a claim for breach of the implied covenant of good faith and fair dealing based on AGFP's termination of nine credit derivative transactions between LBIE and AGFP and asserted claims for breach of contract and breach of the implied covenant of good faith and fair dealing based on AGFP's termination of 28 other credit derivative transactions between LBIE and AGFP and AGFP's calculation of the termination payment in connection with those 28 other credit derivative transactions. Following defaults by LBIE, AGFP properly terminated the transactions in question in compliance with the agreement between AGFP and LBIE, and calculated the termination payment properly. AGFP calculated that LBIE owes AGFP approximately $29 million in connection with the termination of the credit derivative transactions, whereas LBIE asserted in the complaint that AGFP owes LBIE a termination payment of approximately $1.4 billion. AGFP filed a motion to dismiss the claims for breach of the implied covenant of good faith in LBIE's complaint, and on March 15, 2013, the court granted AGFP's motion to dismiss in respect of the count relating to the nine credit derivative transactions and narrowed LBIE's claim with respect to the 28 other credit derivative transactions. LBIE's administrators disclosed in an April 10, 2015 report to LBIE’s unsecured creditors that LBIE's valuation expert has calculated LBIE's claim for damages in aggregate for the 28 transactions to range between a minimum of approximately $200 million and a maximum of approximately $500 million, depending on what adjustment, if any, is made for AGFP's credit risk and excluding any applicable interest. AGFP filed a motion for summary judgment on the remaining causes of action asserted by LBIE and on AGFP's counterclaims, and on July 2, 2018, the court granted in part and denied in part AGFP’s motion. The court dismissed, in its entirety, LBIE’s remaining claim for breach of the implied covenant of good faith and fair dealing and also dismissed LBIE’s claim for breach of contract solely to the extent that it is based upon AGFP’s conduct in connection with the auction. With respect to LBIE’s claim for breach of contract, the court held that there are triable issues of fact regarding whether AGFP calculated its loss reasonably and in good faith. On October 1, 2018, AGFP filed an appeal with the Appellate Division of the Supreme Court of the State of New York, First Judicial Department, seeking reversal of the portions of the lower court's ruling denying AGFP’s motion for summary judgment with respect to LBIE’s sole remaining claim for breach of contract.

Commitments and Contingencies

Legal Proceedings

Lawsuits arise in the ordinary course of the Company’s business. It is the opinion of the Company’s management, based upon the information available, that the expected outcome of litigation against the Company, individually or in the aggregate, will not have a material adverse effect on the Company’s financial position or liquidity, although an adverse resolution of litigation against the Company in a fiscal quarter or year could have a material adverse effect on the Company’s results of operations in a particular quarter or year.

In addition, in the ordinary course of their respective businesses, certain of AGL's subsidiaries assert claims in legal proceedings against third parties to recover losses paid in prior periods or prevent losses in the future. For example, the Company has commenced a number of legal actions in the Federal District Court for Puerto Rico to enforce its rights with respect to the obligations it insures of Puerto Rico and various of its related authorities and public corporations. See "Exposure to Puerto Rico" section of Note 4, Outstanding Exposure, for a description of such actions. See "Recovery Litigation" section of Note 5, Expected Loss to be Paid, for a description of recovery litigation unrelated to Puerto Rico. The amounts, if any, the Company will recover in these and other proceedings to recover losses are uncertain, and recoveries, or failure to obtain recoveries, in any one or more of these proceedings during any quarter or year could be material to the Company's results of operations in that particular quarter or year.

The Company also receives subpoenas duces tecum and interrogatories from regulators from time to time.

Litigation

On November 28, 2011, Lehman Brothers International (Europe) (in administration) (LBIE) sued AG Financial Products Inc. (AGFP), an affiliate of AGC which in the past had provided credit protection to counterparties under CDS. AGC acts as the credit support provider of AGFP under these CDS. LBIE’s complaint, which was filed in the Supreme Court of the State of New York, asserted a claim for breach of the implied covenant of good faith and fair dealing based on AGFP's termination of nine credit derivative transactions between LBIE and AGFP and asserted claims for breach of contract and breach of the implied covenant of good faith and fair dealing based on AGFP's termination of 28 other credit derivative transactions between LBIE and AGFP and AGFP's calculation of the termination payment in connection with those 28 other credit derivative transactions. Following defaults by LBIE, AGFP properly terminated the transactions in question in compliance with the agreement between AGFP and LBIE, and calculated the termination payment properly. AGFP calculated that LBIE owes AGFP approximately $29 million in connection with the termination of the credit derivative transactions, whereas LBIE asserted in the complaint that AGFP owes LBIE a termination payment of approximately $1.4 billion. AGFP filed a motion to dismiss the claims for breach of the implied covenant of good faith in LBIE's complaint, and on March 15, 2013, the court granted AGFP's motion to dismiss in respect of the count relating to the nine credit derivative transactions and narrowed LBIE's claim with respect to the 28 other credit derivative transactions. LBIE's administrators disclosed in an April 10, 2015 report to LBIE’s unsecured creditors that LBIE's valuation expert has calculated LBIE's claim for damages in aggregate for the 28 transactions to range between a minimum of approximately $200 million and a maximum of approximately $500 million, depending on what adjustment, if any, is made for AGFP's credit risk and excluding any applicable interest. AGFP filed a motion for summary judgment on the remaining causes of action asserted by LBIE and on AGFP's counterclaims, and on July 2, 2018, the court granted in part and denied in part AGFP’s motion. The court dismissed, in its entirety, LBIE’s remaining claim for breach of the implied covenant of good faith and fair dealing and also dismissed LBIE’s claim for breach of contract solely to the extent that it is based upon AGFP’s conduct in connection with the auction. With respect to LBIE’s claim for breach of contract, the court held that there are triable issues of fact regarding whether AGFP calculated its loss reasonably and in good faith. On October 1, 2018, AGFP filed an appeal with the Appellate Division of the Supreme Court of the State of New York, First Judicial Department, seeking reversal of the portions of the lower court's ruling denying AGFP’s motion for summary judgment with respect to LBIE’s sole remaining claim for breach of contract.