Redeemable Noncontrolling Interest - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Noncontrolling Interest [Line Items]
Redemption amount of noncontrolling interest	$ 62.5	$ 131.4
Class A Common Stock [Member]
Noncontrolling Interest [Line Items]
Number of days used to determine exchange value based on weighted average price of Class A common stock	20 days
Class A Common Stock [Member] | Exchange of Redeemable Non controlling Interest To Class A Common Stock [Member]
Noncontrolling Interest [Line Items]
Stock conversion ratio	1.00
vTv Therapeutics LLC [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interest ownership percentage	53.20%