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Municipal Bond Guarantee Insurance - Schedule of BAM's Future Expected Premium Revenues (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
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Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |
Total gross unearned insurance premiums | $ 136.8 | $ 82.9
BAM |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |
January 1, 2018 - March 31, 2018 | 2.9 |
April 1, 2018 - June 30, 2018 | 2.9 |
July 1, 2018 - September 30, 2018 | 2.9 |
October 1, 2018 - December 31, 2018 | 2.8 |
Total | 11.5 |
2019 | 11.1 |
2020 | 10.7 |
2021 | 10.2 |
2022 | 9.7 |
2023 and thereafter | 83.6 |
Total gross unearned insurance premiums | $ 136.8 |

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- Definition Amount of unearned premium revenue under contracts issued by an insurance entity that provide protection to the holder of a financial obligation from a financial loss in the event of a default. + References No definition available. + Details
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- Definition Amount of premium revenue under financial guarantee insurance contracts expected to be recognized in the next fiscal quarter following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291 + Details
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- Definition Amount of premium revenue under financial guarantee insurance contracts expected to be recognized in the fourth fiscal quarter following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291 + Details
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- Definition Amount of premium revenue under financial guarantee insurance contracts expected to be recognized in the second fiscal quarter following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291 + Details
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- Definition Amount of premium revenue under financial guarantee insurance contracts expected to be recognized in the third fiscal quarter following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291 + Details
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- Definition Amount of premium revenue under financial guarantee insurance contracts expected to be recognized in the sixth through tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 4 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291 + Details
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- Definition Amount of premium revenue under financial guarantee insurance contracts expected to be recognized in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291 + Details
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- Definition Amount of premium revenue under financial guarantee insurance contracts expected to be recognized in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291 + Details
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- Definition Amount of premium revenue under financial guarantee insurance contracts expected to be recognized in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References No definition available. + Details
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