Discontinued operations - Schedule of Gain (Loss) on Disposal Activity (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2015	Jun. 30, 2015
Loss On Disposal Of Discontinued Operations [Line Items]
Loss on disposal of discontinued operations	$ (41,471)	$ (41,471)
Advertising Business [Member]
Loss On Disposal Of Discontinued Operations [Line Items]
Write-off of goodwill		(35,472)
Write-off of intangible assets		(4,080)
Write-off of long-term deferred assets		(517)
Lease agreements early termination compensation expenses		(1,211)
Employee severance compensation expenses		(191)
Loss on disposal of discontinued operations	$ (41,471)	$ (41,471)

Amount before tax of gain (loss) not previously recognized resulting from the disposal of a discontinued operation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 3B
-URI http://asc.fasb.org/extlink&oid=65878427&loc=SL51721525-107759

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1361-107760

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=65878427&loc=d3e957-107759

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