Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Line Items]
Prepaid expenses and income taxes			$ 1,160,000	$ 1,962,000
Income taxes due included in accounts and income taxes payable			73,000
Recognizes interest and penalties related to uncertain tax positions			22,000	(53,000)	$ 35,000
Accrued interest and penalties related to uncertain tax positions			$ 216,000	$ 194,000	$ 247,000
Reduction of corporate federal income tax rate		35.00%	21.00%
Newly enacted corporate federal income tax rate	21.00%
Effective tax rate as a percentage			24.00%
Earliest Tax Year [Member]
Income Tax Disclosure [Line Items]
Tax fiscal years open to examination			2015
Latest Tax Year [Member]
Income Tax Disclosure [Line Items]
Tax fiscal years open to examination			2018