Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended									12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Revenue from Contract with Customer, Excluding Assessed Tax	$ 216,733	$ 217,415	$ 217,142	$ 224,992	$ 214,140		$ 208,725	$ 212,828	$ 203,726	$ 876,282	$ 839,419	$ 637,123
Net income per share - diluted (in dollars per share)	$ 0.83	$ (0.03)	$ 0.67	$ 0.33	$ 0.36		$ (0.46)	$ 0.54	$ 0.51	$ 1.80	$ 0.95	$ 0.43
Earnings Per Share, Basic	$ 0.84	$ (0.03)	$ 0.68	$ 0.33	$ 0.37		$ (0.46)	$ 0.55	$ 0.52	$ 1.83	$ 0.97	$ 0.44
Net income (loss)	$ 19,741	$ (782)	$ 15,912	$ 7,706	$ 8,466	[1]	$ (10,565)	$ 12,508	$ 11,656
Income from operations	24,468	6,646	24,825	13,503	15,807		13,710	19,219	19,595	$ 69,442	$ 68,331	$ 23,725
Gross profit	$ 76,045	$ 73,405	$ 75,900	$ 79,647	$ 74,716		$ 69,137	$ 71,778	$ 69,430	$ 304,997	$ 285,061	$ 192,885

[1] . Selected Quarterly Financial Data (Unaudited)Below is selected quarterly financial data for fiscal 2019 and 2018: Three Months Ended June 30, 2018 September 30, 2018 December 31, 2018 March 31, 2019Net sales $224,992 $217,142 $217,415 $216,733Gross profit 79,647 75,900 73,405 76,045Income from operations 13,503 24,825 6,646 24,468Net income (loss) $7,706 $15,912 $(782) $19,741 Net income (loss) per share – basic $0.33 $0.68 $(0.03) $0.84 Net income (loss) per share – diluted $0.33 $0.67 $(0.03) $0.83 Three Months Ended June 30, 2017 September 30, 2017 December 31, 2017 March 31, 2018Net sales $203,726 $212,828 $208,725 $214,140Gross profit 69,430 71,778 69,137 74,716Income from operations 19,595 19,219 13,710 15,807Net income (loss) $11,656 $12,508 $(10,565) $8,466 Net income (loss) per share – basic $0.52 $0.55 $(0.46) $0.37 Net income (loss) per share – diluted $0.51 $0.54 $(0.46) $0.36