Quarterly financial data - Condensed Consolidated Statement of Operations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Interim Reporting [Line Items]
Net Sales	$ 117,365	$ 107,857	$ 113,423	$ 108,936	$ 118,639	$ 111,510	$ 108,216	$ 103,606	$ 447,581	$ 441,971	$ 462,571
Cost of sales	24,944	24,384	27,547	21,378	27,300	23,126	22,755	22,346	98,253	95,527	97,093
Gross profit	92,421	83,473	85,876	87,558	91,339	88,384	85,461	81,260	349,328	346,444	365,478
Operating expense	66,808	64,668	71,578	69,638	83,165	67,417	73,102	116,860	272,692	340,544	299,494
Operating income (loss)	25,613	18,805	14,298	17,920	8,174	20,967	12,359	(35,600)	76,636	5,900	65,984
Net income (loss) from continuing operations, net of tax	16,009	10,574	9,870	8,597	7,652	11,300	6,579	(41,749)	45,050	(16,218)	30,997
Net income (loss) from discontinued operations, net of tax	5,152	(5,558)	(2,616)	810	235	(1,225)	(1,184)	282	(2,212)	(1,892)	13,299
Net income (loss)	21,161	5,016	7,254	9,407	7,887	10,075	5,395	(41,467)	42,838	(18,110)	44,296
Basic:
Net income (loss) from continuing operations, net of tax	$ 0.83	$ 0.55	$ 0.52	$ 0.46	$ 0.42	$ 0.61	$ 0.36	$ (2.33)	$ 2.37	$ (0.89)	$ 1.76
Net income (loss) from discontinued operations, net of tax	$ 0.27	$ (0.29)	$ (0.14)	$ 0.04	$ 0.01	$ (0.07)	$ (0.07)	$ 0.02	$ (0.12)	$ (0.10)	$ 0.76
Net income (loss)	$ 1.10	$ 0.26	$ 0.38	$ 0.50	$ 0.43	$ 0.54	$ 0.29	$ (2.31)	$ 2.25	$ (0.99)	$ 2.52
Diluted:
Net income (loss) from continuing operations, net of tax	$ 0.81	$ 0.54	$ 0.51	$ 0.45	$ 0.41	$ 0.60	$ 0.35	$ (2.33)	$ 2.32	$ (0.89)	$ 1.73
Net income (loss) from discontinued operations, net of tax	$ 0.26	$ (0.29)	$ (0.14)	$ 0.04	$ 0.01	$ (0.06)	$ (0.06)	$ 0.02	$ (0.11)	$ (0.10)	$ 0.74
Net income (loss)	$ 1.07	$ 0.25	$ 0.37	$ 0.49	$ 0.42	$ 0.54	$ 0.29	$ (2.31)	$ 2.21	$ (0.99)	$ 2.47
Previously Reported [Member]
Interim Reporting [Line Items]
Net Sales	112,035	114,752	119,492	116,041	123,085	117,306	116,670	113,060	462,320	470,121	460,629
Cost of sales	18,504	22,373	23,676	21,939	23,239	23,854	23,186	22,340	86,492	92,619	90,461
Gross profit	93,531	92,379	95,816	94,102	99,846	93,452	93,484	90,720	375,828	377,502	370,168
Operating expense	69,050	70,846	75,251	71,671	84,035	69,853	74,088	118,217	286,818	346,193	303,918
Operating income (loss)	24,481	21,533	20,565	22,431	15,811	23,599	19,396	(27,497)	89,010	31,309	66,250
Net income (loss) from continuing operations, net of tax	14,636	13,118	13,967	12,215	11,530	12,951	10,519	(36,740)	53,936	(1,740)	27,758
Net income (loss) from discontinued operations, net of tax	5,878	(5,558)	(2,762)	(199)	862	(573)	(561)	939	(2,641)	667	16,450
Net income (loss)	20,514	7,560	11,205	12,016	12,392	12,378	9,958	(35,801)	51,295	(1,073)
Basic:
Net income (loss) from continuing operations, net of tax	$ 0.76	$ 0.69	$ 0.74	$ 0.65	$ 0.62	$ 0.70	$ 0.58	$ (2.05)	$ 2.84	$ (0.10)	$ 1.58
Net income (loss) from discontinued operations, net of tax	$ 0.30	$ (0.29)	$ (0.15)	$ (0.01)	$ 0.05	$ (0.03)	$ (0.03)	$ 0.05	$ (0.14)	$ 0.04	$ 0.93
Net income (loss)	$ 1.06	$ 0.40	$ 0.59	$ 0.64	$ 0.67	$ 0.67	$ 0.55	$ (2.00)	$ 2.70	$ (0.06)	$ 2.51
Diluted:
Net income (loss) from continuing operations, net of tax	$ 0.74	$ 0.67	$ 0.73	$ 0.64	$ 0.62	$ 0.69	$ 0.57	$ (2.05)	$ 2.78	$ (0.10)	$ 1.55
Net income (loss) from discontinued operations, net of tax	$ 0.30	$ (0.28)	$ (0.15)	$ (0.01)	$ 0.04	$ (0.03)	$ (0.03)	$ 0.05	$ (0.14)	$ 0.04	$ 0.92
Net income (loss)	$ 1.04	$ 0.39	$ 0.58	$ 0.63	$ 0.66	$ 0.66	$ 0.54	$ (2.00)	$ 2.64	$ (0.06)	$ 2.47
Adjustments [Member]
Interim Reporting [Line Items]
Net Sales	5,330	(6,895)	(6,069)	(7,105)	(4,446)	(5,796)	(8,454)	(9,454)	(14,739)	(28,150)	1,942
Cost of sales	6,440	2,011	3,871	(561)	4,061	(728)	(431)	6	11,761	2,908	6,632
Gross profit	(1,110)	(8,906)	(9,940)	(6,544)	(8,507)	(5,068)	(8,023)	(9,460)	(26,500)	(31,058)	(4,690)
Operating expense	(2,242)	(6,178)	(3,673)	(2,033)	(870)	(2,436)	(986)	(1,357)	(14,126)	(5,649)	(4,424)
Operating income (loss)	1,132	(2,728)	(6,267)	(4,511)	(7,637)	(2,632)	(7,037)	(8,103)	(12,374)	(25,409)	(266)
Net income (loss) from continuing operations, net of tax	1,373	(2,544)	(4,097)	(3,618)	(3,878)	(1,651)	(3,940)	(5,009)	(8,886)	(14,478)	3,239
Net income (loss) from discontinued operations, net of tax	(726)		146	1,009	(627)	(652)	(623)	(657)	429	(2,559)	(3,151)
Net income (loss)	$ 647	$ (2,544)	$ (3,951)	$ (2,609)	$ (4,505)	$ (2,303)	$ (4,563)	$ (5,666)	$ (8,457)	$ (17,037)
Basic:
Net income (loss) from continuing operations, net of tax	$ 0.07	$ (0.14)	$ (0.22)	$ (0.19)	$ (0.20)	$ (0.09)	$ (0.22)	$ (0.28)	$ (0.47)	$ (0.79)	$ 0.18
Net income (loss) from discontinued operations, net of tax	$ (0.03)		$ 0.01	$ 0.05	$ (0.04)	$ (0.04)	$ (0.04)	$ (0.03)	$ 0.02	$ (0.14)	$ (0.17)
Net income (loss)	$ 0.04	$ (0.14)	$ (0.21)	$ (0.14)	$ (0.24)	$ (0.13)	$ (0.26)	$ (0.31)	$ (0.45)	$ (0.93)	$ 0.01
Diluted:
Net income (loss) from continuing operations, net of tax	$ 0.07	$ (0.13)	$ (0.22)	$ (0.19)	$ (0.21)	$ (0.09)	$ (0.22)	$ (0.28)	$ (0.46)	$ (0.79)	$ 0.18
Net income (loss) from discontinued operations, net of tax	$ (0.04)	$ (0.01)	$ 0.01	$ 0.05	$ (0.03)	$ (0.03)	$ (0.03)	$ (0.03)	$ 0.03	$ (0.14)	$ (0.18)
Net income (loss)	$ (0.03)	$ (0.14)	$ (0.21)	$ (0.14)	$ (0.24)	$ (0.12)	$ (0.25)	$ (0.31)	$ (0.43)	$ (0.93)