Goodwill and Acquired Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite Lived Intangible Assets [Line Items]
Gross carrying amount of intangible assets	$ 515,463	$ 294,610
Intangible assets amortization expense	$ 28,100	20,900	$ 18,200
Weighted Average Amortization Period (years)	15 years
Eat24, Foodler, OrderUp and payments to Zoomer
Finite Lived Intangible Assets [Line Items]
Acquired other intangible assets	$ 229,989
LABite and Purchase of Other Assets
Finite Lived Intangible Assets [Line Items]
Acquired other intangible assets		$ 48,934
Developed technology, trademark and other intangible assets | Fully amortized assets
Finite Lived Intangible Assets [Line Items]
Gross carrying amount of intangible assets	$ 9,100