Summary of Significant Accounting Policies - Net Income Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income	$ 29,969	$ 9,664	$ 33,675	$ 17,825
Denominator:
Weighted average shares outstanding for basic net income per common share (in shares)	9,082	9,037	9,070	9,175
Effect of dilutive stock options (in shares)	36	89	43	96
Adjusted weighted average shares outstanding for diluted net income per common share (in shares)	9,118	9,126	9,113	9,271
Basic net income per common share (in dollars per share)	$ 3.30	$ 1.07	$ 3.71	$ 1.94
Diluted net income per common share (in dollars per share)	$ 3.29	$ 1.06	$ 3.70	$ 1.92