Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended									12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Net income per share - diluted (in dollars per share)	$ 0.36	$ (0.46)	$ 0.54	$ 0.51	$ (0.22)		$ 0.02	$ 0.33	$ 0.32	$ 0.95	$ 0.43	$ 0.96
Earnings Per Share, Basic	$ 0.37	$ (0.46)	$ 0.55	$ 0.52	$ (0.22)		$ 0.02	$ 0.34	$ 0.32	$ 0.97	$ 0.44	$ 0.98
Net income (loss)	$ 8,466	$ (10,565)	$ 12,508	$ 11,656	$ (4,738)	[1]	$ 505	$ 6,816	$ 6,401
Income (loss) from operations	16,324	14,173	19,587	20,015	(3,164)		5,317	12,619	11,201	$ 70,099	$ 25,973	$ 40,570
Gross profit	74,602	69,045	71,619	69,308	50,335		44,821	49,729	48,047	$ 284,574	$ 192,932	$ 187,263
Net sales	$ 214,140	$ 208,725	$ 212,828	$ 203,726	$ 183,688		$ 152,497	$ 151,925	$ 149,013

[1] 19. Selected Quarterly Financial Data (Unaudited)Below is selected quarterly financial data for fiscal 2018 and 2017: 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 69,308 71,619 69,045 74,602Income (loss) from operations 20,015 19,587 14,173 16,324Net 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 Three Months Ended June 30, 2016 September 30, 2016 December 31, 2016 March 31, 2017Net sales $149,013 $151,925 $152,497 $183,688Gross profit 48,047 49,729 44,821 50,335Income from operations 11,201 12,619 5,317 (3,164)Net income (loss) $6,401 $6,816 $505 $(4,738) Net income (loss) per share – basic $0.32 $0.34 $0.02 $(0.22) Net income (loss) per share – diluted $0.32 $0.33 $0.02 $(0.22)