Summary of Significant Accounting Policies - Investments in Affiliates and Other Entities (Detail) $ in Millions |
3 Months Ended |
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Sep. 30, 2018
USD ($)
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| Water and Gas Pipeline Infrastructure Contractor | |
| Summary Of Significant Accounting Policies [Line Items] | |
| Equity interest acquired | 30.00% |
| Cash subscription price | $ 22.2 |
| Capital for Infrastructure Projects | |
| Summary Of Significant Accounting Policies [Line Items] | |
| Capital provided to investors | 80.0 |
| Infrastructure Investors Partnership | Capital for Infrastructure Projects | |
| Summary Of Significant Accounting Policies [Line Items] | |
| Capital provided to investors | $ 1,000.0 |
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- Definition Equity Securities Without Readily Determinable Fair Value, Ownership Percentage No definition available.
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- Definition Summary Of Significant Accounting Policies [Line Items] No definition available.
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- Definition Amount of investment in equity security without readily determinable fair value. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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. No definition available.
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