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Commitments and Contingencies (Narrative) (Details) | Mar. 31, 2017 USD ($) | Mar. 31, 2017 GBP (£) | Apr. 30, 2016 GBP (£)
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Non-Public Investment Entities [Member] |  |  |
Other Commitment, Fiscal Year Maturity [Abstract] |  |  |
Commitments Total | $ 138,400,000 |  |
Commitments due 2017 | 55,300,000 |  |
Commitments due 2018 and 2019 | 52,800,000 |  |
Commitments due 2020 and 2021 | 25,400,000 |  |
Commitments due thereafter | 4,900,000 |  |
Qualified Affordable Housing Project [Member] |  |  |
Other Commitment, Fiscal Year Maturity [Abstract] |  |  |
Commitments due 2017 | 300,000 |  |
Commitments due 2018 and 2019 | 300,000 |  |
Commitments due 2020 and 2021 | 300,000 |  |
Commitments due thereafter | 500,000 |  |
Qualified affordable housing project investments | 1,400,000 |  |
Strategic Business Partnership [Member] |  |  |
Other Commitment, Fiscal Year Maturity [Abstract] |  |  |
Line of credit amount | 9,000,000 |  |
Line of credit unused commitment | 4,900,000 |  |
Lloyds Syndicate [Member] |  |  |
Other Commitment, Fiscal Year Maturity [Abstract] |  |  |
Required FAL Deposit | 97,700,000 |  |
Current lending capacity under revolving credit agreement | £ |  |  | £ 20,000,000
Interest rate on revolving credit agreement |  |  | 3.80%
Unused commitments to extend credit | 15,600,000 | £ 12,400,000 |
Lloyds Syndicate [Member] | Commitment to Provide Capital [Member] |  |  |
Other Commitment, Fiscal Year Maturity [Abstract] |  |  |
Commitments Total | $ 200,000,000 |  |

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- Definition Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions. + References No definition available. + Details
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- Definition Amount of commitment or contingent commitments to qualified affordable housing project investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=64813897&loc=SL49122993-202985 + Details
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