Earnings Per Share - Schedule of Basic and Diluted Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net (loss) attributable to common shareholders of Party City Holdco Inc.	$ 29,811	$ (130,015)	$ 15,747	$ (671,528)
Weighted average shares - Basic	111,340,295	93,419,078	111,128,822	93,407,344
Effect of dilutive securities:
Warrants	0	0	62,121	0
Restricted stock units	4,568,313		3,971,807
Stock options	342,543	0	336,554	0
Weighted average shares - Diluted	116,251,151	93,419,078	115,499,304	93,407,344
Net income (loss) per share attributable to common shareholders of Party City Holdco Inc.-Basic	$ 0.27	$ (1.39)	$ 0.14	$ (7.19)
Net income (loss) per share attributable to common shareholders of Party City Holdco Inc.-Diluted	$ 0.26	$ (1.39)	$ 0.14	$ (7.19)