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Reconciliation of Our Investment in Restricted Equity Securities Measured at Fair Value on Quarterly Basis Using Significant Unobservable Inputs (Level 3) (Detail) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2020 | Mar. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Balance at beginning of period | $ 55.9 |
Purchases |  | $ 54.7
Unrealized (losses) gains included in earnings | (16.5) | 1.7
Balance at end of period | 39.4 |
Equity Securities | Level 3 | Long-term investments | Fair Value Measurements Recurring |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Balance at beginning of period | 55.9 |
Purchases |  | 54.7
Unrealized (losses) gains included in earnings | (16.5) | 1.7
Balance at end of period | $ 39.4 | $ 56.4

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- Definition Amount of restricted investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729 + Details
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- Definition Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714 + Details
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- Definition The cash outflow to acquire investments (not to include restricted cash) that are pledged or subject to withdrawal restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585 + Details
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