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Income Taxes - Additional Information (Detail) - USD ($) | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2018 | Dec. 31, 2017 | Jun. 30, 2019 | Jun. 30, 2018
Income Tax Contingency [Line Items] |  |  |  |  |  |  |
U.S. federal statutory rate | 21.00% |  |  | 21.00% | 35.00% |  | 28.00%
Tax Act, incomplete accounting, provisional adjustments |  | $ (32,600,000) |  |  |  |  |
Earnings per share increase |  | $ 0.45 |  |  |  |  |
Tax Act, limitation on deduction of executive compensation | $ 1,000,000 |  |  |  |  |  |
Tax Act, incomplete accounting, transition tax for accumulated foreign earnings, provisional income tax expense | 0 |  |  |  |  |  |
Income tax expense | $ 1,600,000 |  | $ 4,500,000 |  |  |  |
Approximate rate on pre-tax income | 200.00% |  | 5.40% |  |  |  |
Scenario, Plan [Member] |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |
U.S. federal statutory rate |  |  |  |  |  | 21.00% |
Foreign Tax Authority [Member] |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |
Tax Act, incomplete accounting, provisional adjustments | $ 0 |  |  |  |  |  |
Foreign Tax Authority [Member] | Earliest Tax Year [Member] | Federal Ministry of Finance, Germany [Member] |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |
Tax year being audited in income tax examination | 2013 |  |  |  |  |  |
Foreign Tax Authority [Member] | Latest Tax Year [Member] | Federal Ministry of Finance, Germany [Member] |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |
Tax year being audited in income tax examination | 2015 |  |  |  |  |  |
State Tax Authority [Member] | Earliest Tax Year [Member] | State of New Jersey [Member] |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |
Tax year being audited in income tax examination | 2013 |  |  |  |  |  |
State Tax Authority [Member] | Latest Tax Year [Member] | State of New Jersey [Member] |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |
Tax year being audited in income tax examination | 2017 |  |  |  |  |  |

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