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Subsequent Event (Details) - Subsequent Event - USD ($) $ in Millions | Feb. 28, 2018 | Feb. 05, 2018 | Jan. 26, 2018 | Jan. 24, 2018
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DavidShield & PassportCard |  |  |  |
Subsequent Event [Line Items] |  |  |  |
Ownership interest (as a percent) |  |  |  | 50.00%
Investment (up to) |  |  |  | $ 28
CrossHarbor |  |  |  |
Subsequent Event [Line Items] |  |  |  |
Investment (up to) |  |  | $ 50 |
Kudu Investment Management, LLC |  |  |  |
Subsequent Event [Line Items] |  |  |  |
Investment (up to) | $ 2 | $ 125 |  |

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- Definition This element represents the aggregate cost of investments accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571 + Details
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Balance Type: | na
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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
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Data Type: | xbrli:stringItemType
Balance Type: | na
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- Details
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- Details
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- Details
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Namespace Prefix: |
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- Details
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