Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Income Taxes - Reconciliation of Unrecognized Tax Benefits and Interest and Penalties (Detail)

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Income Taxes - Reconciliation of Unrecognized Tax Benefits and Interest and Penalties (Detail) - USD ($)
12 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]      
Unrecognized tax benefits, Beginning balance $ 700,000 $ 700,000 $ 4,900,000
Unrecognized tax benefits, Additions for tax positions of the current year 0 100,000 200,000
Unrecognized tax benefits, Reductions in tax positions of prior year 0 (100,000) (4,100,000)
Unrecognized tax benefits, Settlements paid during the current period     (300,000)
Unrecognized tax benefits, Ending Balance 700,000 700,000 700,000
Interest and Penalties, Beginning balance 0 0 300,000
Interest And Penalties, Reductions in tax position of prior year     (300,000)
Interest and Penalties, Ending Balance $ 0 $ 0 $ 0