Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	May 25, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets liabilities transfers between valuation levels		$ 0	$ 0
PuzzleSocial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration obligation	$ 0	0
Gram Games [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration obligation	45,000,000	$ 45,000,000		$ 43,500,000
Contingent consideration payable, total years		3 years
Gram Games [Member] | Research and Development Expense [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration obligation, expense recognized	$ 1,500,000	$ 1,500,000