Quarterly Financial Information (Unaudited) (Detail) - USD ($)		3 Months Ended								12 Months Ended
	Oct. 01, 2020	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Quarterly Financial Information [Line Items]
Revenues		$ 89,990,000	$ 87,952,000	$ 88,566,000	$ 89,528,000	$ 95,163,000	$ 94,300,000	$ 96,888,000	$ 102,294,000	$ 356,036,000	[1]	$ 388,645,000	[1]	$ 419,482,000	[1]
Cost of revenues		43,499,000	46,466,000	44,949,000	45,798,000	46,831,000	47,390,000	51,994,000	53,407,000	180,712,000	[1],[2],[3]	199,622,000	[1],[2],[3]	200,220,000	[1],[2],[3]
Gross profit		46,491,000	41,486,000	43,617,000	43,730,000	48,332,000	46,910,000	44,894,000	48,887,000
Selling and marketing		17,869,000	17,131,000	16,007,000	19,213,000	20,555,000	20,421,000	23,329,000	24,840,000	70,220,000	[2],[3]	89,145,000	[2],[3]	108,395,000	[2],[3]
Research and development		9,304,000	9,501,000	9,765,000	10,136,000	12,639,000	14,064,000	16,883,000	18,216,000	38,706,000	[2],[3]	61,802,000	[2],[3]	76,979,000	[2],[3]
General and administrative		14,363,000	12,136,000	13,741,000	15,543,000	15,878,000	14,064,000	16,932,000	19,545,000	55,783,000	[1],[2],[3]	66,419,000	[1],[2],[3]	84,535,000	[1],[2],[3]
Amortization of intangible assets		6,705,000	6,750,000	6,846,000	6,918,000	6,925,000	6,970,000	8,076,000	8,105,000	27,219,000		30,076,000		32,864,000
Impairment of right-of-use and long-lived assets		0	0	0	4,671,000					4,671,000		0		0
Investigation and audit related						129,000	980,000	2,354,000	842,000	0		4,305,000		38,338,000
Impairment of goodwill	$ 0					0	0	224,272,000	0	0		224,272,000		0
Impairment of intangible asset						0	0	17,308,000	0	0		17,308,000		0
Settlement of litigation, net						0	(2,100,000)	5,000,000	0	0		2,900,000		5,250,000
Restructuring						(1,886,000)	2,270,000	2,949,000	(70,000)	0	[3]	3,263,000	[3]	11,837,000	[3]
Total expenses from operations		48,241,000	45,518,000	46,359,000	56,481,000	54,240,000	56,669,000	317,103,000	71,478,000
Loss from operations		(1,750,000)	(4,032,000)	(2,742,000)	(12,751,000)	(5,908,000)	(9,759,000)	(272,209,000)	(22,591,000)	(21,275,000)		(310,467,000)		(138,936,000)
Interest expense, net		(9,076,000)	(9,027,000)	(8,856,000)	(8,846,000)	(8,350,000)	(8,175,000)	(8,242,000)	(6,759,000)	(35,805,000)	[1]	(31,526,000)	[1]	(16,465,000)	[1]
Other income (expense), net		1,692,000	4,191,000	1,477,000	7,194,000	(4,967,000)	6,733,000	(3,081,000)	2,969,000	14,554,000		1,654,000		(1,464,000)
(Loss) gain from foreign currency transactions		(2,338,000)	(2,012,000)	(944,000)	804,000	(432,000)	1,194,000	(464,000)	38,000	(4,490,000)		336,000		1,303,000
Loss before income taxes		(11,472,000)	(10,880,000)	(11,065,000)	(13,599,000)	(19,657,000)	(10,007,000)	(283,996,000)	(26,343,000)	(47,016,000)		(340,003,000)		(155,562,000)
Income tax (provision) benefit		(1,740,000)	(241,000)	664,000	415,000	(1,733,000)	(552,000)	4,463,000	(1,171,000)	(902,000)		1,007,000		(3,706,000)
Net loss		$ (13,212,000)	$ (11,121,000)	$ (10,401,000)	$ (13,184,000)	$ (21,390,000)	$ (10,559,000)	$ (279,533,000)	$ (27,514,000)	$ (47,918,000)		$ (338,996,000)		$ (159,268,000)
Net loss per common share:
Basic and diluted (in dollars per share)		$ (0.18)	$ (0.16)	$ (0.15)	$ (0.19)	$ (0.31)	$ (0.16)	$ (4.61)	$ (0.46)	$ (0.67)		$ (5.33)		$ (2.76)
Weighted-average number of shares used in per share calculation - Common Stock:
Basic and diluted (in shares)		72,814,261	71,222,122	70,554,326	70,127,939	69,644,437	64,157,167	60,697,608	59,958,203	71,181,496		63,590,882		57,700,603
Stock-based compensation expense		$ 2,545,000	$ 2,524,000	$ 2,346,000	$ 2,658,000	$ 2,425,000	$ 3,142,000	$ 4,038,000	$ 6,953,000	$ 10,073,000		$ 16,558,000		$ 37,619,000
Cost of revenues
Weighted-average number of shares used in per share calculation - Common Stock:
Stock-based compensation expense		89,000	503,000	487,000	209,000	(28,000)	396,000	636,000	848,000	1,288,000		1,852,000		6,349,000
Selling and marketing
Weighted-average number of shares used in per share calculation - Common Stock:
Stock-based compensation expense		272,000	625,000	720,000	609,000	456,000	756,000	1,087,000	1,316,000	2,226,000		3,615,000		9,452,000
Research and development
Weighted-average number of shares used in per share calculation - Common Stock:
Stock-based compensation expense		69,000	386,000	375,000	56,000	118,000	469,000	668,000	726,000	886,000		1,981,000		6,580,000
General and administrative
Weighted-average number of shares used in per share calculation - Common Stock:
Stock-based compensation expense		$ 2,115,000	$ 1,010,000	$ 764,000	$ 1,784,000	1,879,000	1,392,000	1,913,000	4,063,000	5,673,000		9,247,000		14,770,000
Restructuring
Weighted-average number of shares used in per share calculation - Common Stock:
Stock-based compensation expense						$ 0	$ 129,000	$ (266,000)	$ 0	$ 0		$ (137,000)		$ 468,000

[1] Transactions with related parties are included in the line items above as follows (refer to Footnote 13, Related Party Transactions, of the Notes to Consolidated Financial Statements for additional information): Years Ended December 31,202020192018Revenues$13,314 $17,464 $12,662 Cost of revenues10,094 10,490 11,239 General and administrative316 776 650 Interest expense, net(24,480)(23,494)(16,023)

[2] Excludes amortization of intangible assets, which is presented separately in the Consolidated Statements of Operations and Comprehensive Loss.

[3] Stock-based compensation expense is included in the line items above as follows: Years Ended December 31,202020192018Cost of revenues$1,288 $1,852 $6,349 Selling and marketing2,226 3,615 9,452 Research and development886 1,981 6,580 General and administrative5,673 9,247 14,770 Restructuring— (137)468 Total stock-based compensation expense$10,073 $16,558 $37,619