Line of Credit (Details) - USD ($)	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015	Jan. 04, 2016
Line of Credit Facility [Line Items]
Line of credit	$ 15,000,000	$ 105,000,000
Remaining borrowing capacity	$ 235,000,000	$ 145,000,000
Line of Credit Facility, Interest Rate at Period End	2.3125%	2.40%
Interest expense	$ 1,899,000
Debt, Weighted Average Interest Rate	2.35%	3.20%
Debt Instrument, Fee Amount		$ 5,382,000
Amortization of debt issuance costs	$ (1,076,000)	$ (258,000)	$ 0
Line of Credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 250,000
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity				10,000
Swing-Line Loans [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 10,000