Overview and Summary of Significant Accounting Policies - Additional Information (Detail)		3 Months Ended	12 Months Ended
	Jan. 02, 2016	Sep. 30, 2016 USD ($)	Dec. 31, 2017 USD ($) Segment Financial_Institution	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) $ / shares
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Initial offering period			December 2011
Changes in revenue from adjustments of prior period deferred revenue			$ 1,300,000	$ 100,000	$ 1,000,000
Revenue and income from operations				4,000,000	$ 9,900,000
Impact on reported earnings per share | $ / shares					$ 0.01
Operating segment | Segment			1
Reportable segment | Segment			1
Impairments of short-term investments			$ 0
Impairment of intangible assets				$ 20,677,000
Expected dividend yield			0.00%	0.00%	0.00%
Income tax benefit in connection with re-measurement of deferred tax assets and liabilities			$ 2,400,000
Income tax benefit in connection with refundable AMT credit			$ 2,600,000
Number of financial institutions in which cash, cash equivalents and securities held | Financial_Institution			3
Advertising expense			$ 147,200,000	$ 132,500,000	$ 128,900,000
FASB issued ASU 2016-09
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative effect adjustment to retained earnings (a reduction in the accumulated deficit)			48,200,000
Valuation allowance, deferred tax asset, increase (decrease), amount			97,300,000
Cumulative effect adjustment to retained earnings (an increase in the accumulated deficit)			$ 3,900,000
Facebook [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Entity wide accounts receivables major customer percentage			10.00%	12.00%
Apple [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Entity wide accounts receivables major customer percentage			34.00%	27.00%
Google [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Entity wide accounts receivables major customer percentage			19.00%	23.00%
MoPub [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Entity wide accounts receivables major customer percentage			15.00%	10.00%
Acquired Intangible Assets [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Impairment of intangible assets			$ 0		$ 0
Rising Tide [Member] | Developed Technology [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Impairment of intangible assets		$ 18,200,000
Zindagi [Member] | Developed Technology [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Estimated useful lives of intangible assets	3 years
Impairment of intangible assets		$ 2,500,000
Minimum [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Estimated useful lives of intangible assets			12 months
Minimum [Member] | FASB issued ASU 2014-09 [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Transition adjustment			$ 3,000,000
Maximum [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Estimated useful lives of intangible assets			84 months
Maximum [Member] | FASB issued ASU 2014-09 [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Transition adjustment			$ 5,000,000
Consumable Virtual Goods [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenue recognition period			1 month
Facebook Credits [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Percentage of revenue recognized price			70.00%