Correction of Immaterial Misstatements in Prior Period Financial Statements - Summary of Impact, by Financial Statement (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 01, 2018	Dec. 31, 2015
Consolidated Balance Sheet
Goodwill	$ 74,292				$ 70,729				$ 74,292	$ 70,729	$ 50,081
Total assets	690,409				766,139				690,409	766,139	517,921
Accounts payable and accrued expenses	51,034				61,847				51,034	61,847
Total current liabilities	54,034				64,847				54,034	64,847
Other long-term liabilities	16,418				19,889				16,418	19,889
Total liabilities	357,677				417,864				357,677	417,864
Accumulated deficit	(528,164)				(540,325)				(528,164)	(540,325)
Total stockholders' equity	332,732				348,275				332,732	348,275	183,456		$ 167,273
Total liabilities and stockholders' equity	690,409				766,139				690,409	766,139
Consolidated Statement of Operations
Total expenses									264,238	258,173	209,658
Operating income									33,577	277,861	48,856
Income (loss) before income taxes									21,412	258,620	33,526
Income tax (expense) benefit									(7,877)	(82,612)	(13,121)
Income (loss) before equity in net income (loss) of nonconsolidated affiliate									13,535	176,008	20,405
Net income	$ 6,913	$ 2,215	$ 4,840	$ (1,807)	$ 12,740	$ 157,014	$ 3,326	$ 2,618	$ 12,161	$ 175,698	$ 20,405
Net income per share, diluted	$ 0.08	$ 0.02	$ 0.05	$ (0.02)	$ 0.14	$ 1.70	$ 0.04	$ 0.03	$ 0.13	$ 1.91	$ 0.22
Consolidated Statement of Comprehensive Income
Net income	$ 6,913	$ 2,215	$ 4,840	$ (1,807)	$ 12,740	$ 157,014	$ 3,326	$ 2,618	$ 12,161	$ 175,698	$ 20,405
Comprehensive income									10,809	178,615	21,543
Consolidated Statement of Stockholders' Equity
Net income	6,913	2,215	4,840	(1,807)	12,740	157,014	3,326	2,618	12,161	175,698	20,405
Accumulated deficit	(528,164)				(540,325)				(528,164)	(540,325)
Total stockholders' equity	332,732				348,275				332,732	348,275	183,456		$ 167,273
Consolidated Statement of Cash Flows
Net income	6,913	$ 2,215	$ 4,840	$ (1,807)	12,740	$ 157,014	$ 3,326	$ 2,618	12,161	175,698	20,405
Deferred income taxes									4,612	81,766	12,528
Increase (decrease) in accounts payable, accrued expenses and other liabilities									(9,727)	2,825	1,203
Purchase of a businesses, net of cash acquired									(3,522)	(29,149)
Net cash used in investing activities									(159,546)	(76,405)	(9,553)
Payment of contingent consideration									(2,015)	(3,819)
Net cash used in financing activities									(88,628)	(24,795)	(34,147)
Contingent consideration included in accounts payable, accrued expenses and other liabilities									8,119	12,107
Digital Media
Consolidated Balance Sheet
Goodwill	33,743				30,180				33,743	30,180	14,169	$ 33,700
Total assets	$ 81,460				82,949				81,460	82,949	24,244
Consolidated Statement of Operations
Cost of revenue									$ 45,096	32,998	$ 9,536
As Previously Reported
Consolidated Balance Sheet
Goodwill					70,557					70,557
Total assets					765,967					765,967
Accounts payable and accrued expenses					59,522					59,522
Total current liabilities					62,522					62,522
Other long-term liabilities					21,447					21,447
Total liabilities					417,097					417,097
Accumulated deficit					(539,730)					(539,730)
Total stockholders' equity					348,870					348,870
Total liabilities and stockholders' equity					765,967					765,967
Consolidated Statement of Operations
Total expenses										257,381
Operating income										278,653
Income (loss) before income taxes										259,412
Income tax (expense) benefit										(82,809)
Income (loss) before equity in net income (loss) of nonconsolidated affiliate										176,603
Net income										$ 176,293
Net income per share, diluted										$ 1.92
Consolidated Statement of Comprehensive Income
Net income										$ 176,293
Comprehensive income										179,210
Consolidated Statement of Stockholders' Equity
Net income										176,293
Accumulated deficit					(539,730)					(539,730)
Total stockholders' equity					348,870					348,870
Consolidated Statement of Cash Flows
Net income										176,293
Deferred income taxes										81,963
Increase (decrease) in accounts payable, accrued expenses and other liabilities										2,033
Purchase of a businesses, net of cash acquired										(32,968)
Net cash used in investing activities										(80,224)
Net cash used in financing activities										(20,976)
Contingent consideration included in accounts payable, accrued expenses and other liabilities										15,926
As Previously Reported | Digital Media
Consolidated Statement of Operations
Cost of revenue										32,206
Adjustment
Consolidated Balance Sheet
Goodwill					172					172
Total assets					172					172
Accounts payable and accrued expenses					2,325					2,325
Total current liabilities					2,325					2,325
Other long-term liabilities					(1,558)					(1,558)
Total liabilities					767					767
Accumulated deficit					(595)					(595)
Total stockholders' equity					(595)					(595)
Total liabilities and stockholders' equity					172					172
Consolidated Statement of Operations
Total expenses										792
Operating income										(792)
Income (loss) before income taxes										(792)
Income tax (expense) benefit										197
Income (loss) before equity in net income (loss) of nonconsolidated affiliate										(595)
Net income										$ (595)
Net income per share, diluted										$ (0.01)
Consolidated Statement of Comprehensive Income
Net income										$ (595)
Comprehensive income										(595)
Consolidated Statement of Stockholders' Equity
Net income										(595)
Accumulated deficit					(595)					(595)
Total stockholders' equity					$ (595)					(595)
Consolidated Statement of Cash Flows
Net income										(595)
Deferred income taxes										(197)
Increase (decrease) in accounts payable, accrued expenses and other liabilities										792
Purchase of a businesses, net of cash acquired										3,819
Net cash used in investing activities										3,819
Payment of contingent consideration										(3,819)
Net cash used in financing activities										(3,819)
Contingent consideration included in accounts payable, accrued expenses and other liabilities										(3,819)
Adjustment | Digital Media
Consolidated Statement of Operations
Cost of revenue										$ 792