Earnings Per Share - Schedule of Reconciliation Between Basic and Diluted Income Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net (loss) income attributable to common shareholders of Party City Holdco Inc.	$ (2,420)	$ 10,084	$ 24,934	$ 30,383
Weighted average shares - Basic	96,494,565	119,587,339	96,449,011	119,546,451
Effect of dilutive securities:
Warrants	0	0	0	0
Restricted stock units			9,004
Stock options		1,325,510	1,226,275	1,361,528
Weighted average shares - Diluted	96,494,565	120,912,849	97,684,290	120,907,979
Net (loss) income per share attributable to common shareholders of Party City Holdco Inc. - Basic	$ (0.03)	$ 0.08	$ 0.26	$ 0.25
Net (loss) income per share attributable to common shareholders of Party City Holdco Inc. - Diluted	$ (0.03)	$ 0.08	$ 0.26	$ 0.25