Schedule I - Condensed Financial Information of Registrant - Condensed Statements of Operations and Comprehensive (Loss) Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Income Statements Captions [Line Items]
Net (loss) income	$ (96,395)	$ 239,665	$ (130,059)	$ (541,668)	$ (268,829)	$ (281,745)	$ 48,005	$ (30,289)	$ (528,457)	$ (532,858)	$ 122,819
Add: Net income attributable to redeemable securities holder											409
Net (loss) income attributable to common shareholders of Party City Holdco Inc	$ (96,417)	$ 239,707	$ (130,015)	$ (541,513)	$ (268,818)	$ (281,533)	$ 48,074	$ (30,218)	(528,238)	(532,495)	123,259
Other comprehensive (loss) income, net									5,791	13,444	(13,416)
Comprehensive income									(522,666)	(519,414)	109,403
Comprehensive income attributable to redeemable securities holder											409
Comprehensive (loss) income attributable to common shareholders of Party City Holdco Inc.									(522,420)	(519,028)	109,876
Party City Holdco Inc. [Member]
Condensed Income Statements Captions [Line Items]
Equity in net income of subsidiaries									(528,238)	(532,495)	122,850
Net (loss) income									(528,238)	(532,495)	122,850
Add: Net income attributable to redeemable securities holder											409
Net (loss) income attributable to common shareholders of Party City Holdco Inc									(528,238)	(532,495)	123,259
Other comprehensive (loss) income, net									5,818	13,467	(13,383)
Comprehensive income									(522,420)	(519,028)	109,467
Comprehensive income attributable to redeemable securities holder											409
Comprehensive (loss) income attributable to common shareholders of Party City Holdco Inc.									$ (522,420)	$ (519,028)	$ 109,876