Contract Liabilities (Details) - USD ($)	Sep. 30, 2018	Mar. 31, 2018
Short-term contract liabilities [Abstract]
Customer allowances earned	$ 11,381,000	$ 11,370,000
Customer core returns accruals	4,743,000	4,697,000
Accrued core payment, net	15,364,000	16,536,000
Total short-term contract liabilities	31,488,000	32,603,000
Long-term contract liabilities [Abstract]
Customer core returns accruals	34,000,000	29,710,000
Accrued core payment, net	18,535,000	18,473,000
Total long-term contract liabilities	52,535,000	48,183,000
Total contract liabilities	$ 84,023,000	$ 80,786,000