Commitments and Contingencies - Purchase Commitments (Details)	12 Months Ended
	Mar. 31, 2019 USD ($)
Future commitments
Outstanding purchase orders	$ 424,274,000
Minimum
Future commitments
Advance purchase period	4 months
Maximum
Future commitments
Advance purchase period	9 months
Sheepskin
Future commitments
Remaining Commitment	$ 208,577,000
Long-term purchase commitment period	2 years
Advance deposit	$ 0
Contract Value	250,870,000
Sheepskin Purchase Commitment One
Future commitments
Remaining Commitment	25,792,000
Contract Value	45,600,000
Sheepskin Purchase Commitment Two
Future commitments
Remaining Commitment	18,300,000
Contract Value	26,800,000
Sheepskin Purchase Commitment Three
Future commitments
Remaining Commitment	10,515,000
Contract Value	24,500,000
Sheepskin Purchase Commitment Four
Future commitments
Remaining Commitment	14,160,000
Contract Value	14,160,000
Sheepskin Purchase Commitment Five
Future commitments
Remaining Commitment	54,600,000
Contract Value	54,600,000
Sheepskin Purchase Commitment Six
Future commitments
Remaining Commitment	34,750,000
Contract Value	34,750,000
Sheepskin Purchase Commitment Seven
Future commitments
Remaining Commitment	50,460,000
Contract Value	50,460,000
Other Purchase Commitment
Future commitments
Long-term purchase commitment	$ 52,302,000