Other Income, Net - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Other Income and Expenses [Abstract]
Proceeds from sales / distributions of ownership interests	$ 30		$ 60	$ 1,000
Realized gain from cost-method investment	2,800		2,800
Loan repayment from equity method investment			16	400
Discontinued operations, held-for-sale | GovDelivery
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Increase (decrease) to other (loss) income	$ 68	$ 44	$ 186	$ 49