Selected Quarterly Financial Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended									12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014		Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 148,929	$ 140,791	$ 146,991	$ 142,932	$ 160,475		$ 145,072	$ 138,852	$ 138,891
Gross profit	45,477	43,409	47,156	45,565	50,300		42,997	44,260	43,491	181,607	181,048	174,231
Income from operations	12,893	12,615	16,134	13,006	17,527		11,101	12,286	13,436	54,648	54,350	54,371
Net income	$ 1,997	$ 7,861	$ 10,599	$ 6,733	$ 9,615	[1]	$ 6,664	$ 7,122	$ 7,020
Net income per share - basic (in dollars per share)	$ 0.10	$ 0.39	$ 0.53	$ 0.34	$ 0.49		$ 0.34	$ 0.36	$ 0.36	$ 1.36	$ 1.55	$ 4.03
Net income per share - diluted (in dollars per share)	$ 0.08	$ 0.39	$ 0.53	$ 0.34	$ 0.48		$ 0.33	$ 0.36	$ 0.35	$ 1.34	$ 1.52	$ 3.98

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