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Investments - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Mar. 31, 2019 | Dec. 31, 2019 | Dec. 31, 2018 | Jan. 01, 2018
Schedule of Investments [Line Items] |  |  |  |
Transfer to investments | $ 3.4 |  |  |
Carrying value |  | $ 3.4 |  |
Other Receivables [Member] |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Note receivable |  | $ 0.9 | $ 4.3 |
ASU 2016-01 [Member] |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Reclassification of net unrealized gains of marketable equity securities from AOCI to retained earnings |  |  |  | $ 3.2
Investment [Member] | Issuer Concentration [Member] | Market Value of Total Investment Portfolio [Member] |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Investment concentration risk percentage |  | 5.00% |  |

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