Auction Rate Securities - Narrative (Details)
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6 Months Ended |
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May 16, 2018
USD ($)
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Apr. 30, 2018
USD ($)
institution
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Oct. 31, 2017
USD ($)
institution
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| Schedule of Available-for-sale Securities [Line Items] |
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| Number of different auction rate securities issuers | institution |
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2
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2
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| Interest rate reset interval |
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30 days
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| Auction Rate Securities |
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| Schedule of Available-for-sale Securities [Line Items] |
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| Investment in auction rate securities, original principal amount |
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$ 10,000,000
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$ 10,000,000
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| Investment in auction rate securities, amortized cost basis |
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8,000,000
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8,000,000
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| Investment in auction rate securities, fair value |
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8,000,000
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8,000,000
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| Unrealized holding gain (loss) on securities |
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0
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0
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| Auction Rate Securities | Retained Earnings |
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| Schedule of Available-for-sale Securities [Line Items] |
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| Total amount of other-than-temporary impairment (OTTI) credit loss recognized |
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$ 2,000,000
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$ 2,000,000
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| Subsequent Event | Auction Rate Securities |
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| Schedule of Available-for-sale Securities [Line Items] |
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| Investment in auction rate securities, amortized cost basis |
$ 3,000,000
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| Available-for-sale debt securities, original par value |
5,000,000
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| Proceeds from sale of AFS securities, debt |
$ 2,900,000
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