Quarterly Results (Unaudited) - Summary of Historical Revenues Gross Profit Income (Loss) From Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Net sales									$ 2,339,510
Gross profit	$ 293,239	$ 164,932	$ 208,646	$ 172,060	$ 363,119	$ 201,199	$ 228,624	$ 188,142
(Loss) Income from operations	(227,055)	(277,526)	97,485	(10,297)	158,840	31,738	65,451	22,256	(417,393)	$ 278,285	$ 280,136
Net (loss) income	(268,829)	(281,745)	48,005	(30,289)	98,374	(2,440)	28,048	(1,163)	(532,858)	122,819	215,340
Net (loss) income attributable to common shareholders of Party City Holdco Inc.	$ (268,818)	$ (281,533)	$ 48,074	$ (30,218)	$ 98,325	$ (2,420)	$ 28,487	$ (1,133)	$ (532,495)	$ 123,259	$ 215,340
Net (loss) income per share attributable to common shareholders of Party City Holdco Inc.-Basic	$ (2.88)	$ (3.02)	$ 0.52	$ (0.32)	$ 1.03	$ (0.03)	$ 0.30	$ (0.01)	$ (5.71)	$ 1.28	$ 1.81
Net (loss) income per share attributable to common shareholders of Party City Holdco Inc.-Diluted	$ (2.88)	$ (3.02)	$ 0.51	$ (0.32)	$ 1.02	$ (0.03)	$ 0.29	$ (0.01)	$ (5.71)	$ 1.27	$ 1.79
Net Sales [Member]
Revenues:
Net sales	$ 728,361	$ 538,345	$ 561,702	$ 511,102	$ 802,393	$ 550,840	$ 558,101	$ 505,108		$ 2,416,442	$ 2,357,986
Royalties and Franchise Fees [Member]
Revenues:
Net sales	$ 3,190	$ 1,886	$ 2,189	$ 2,014	$ 3,241	$ 2,206	$ 2,910	$ 2,716	$ 9,279	$ 11,073	$ 13,583