Earnings Per Share - Schedule of Reconciliation Between Basic and Diluted Income Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net income attributable to common shareholders of Party City Holdco Inc.	$ 28,487	$ 24,982	$ 27,354	$ 20,299
Weighted average shares - Basic	96,453,884	119,528,147	96,426,235	119,526,007
Effect of dilutive securities:
Warrants	0	0	0	0
Restricted stock units	0	0	0	0
Stock options	1,234,350	1,415,598	1,243,074	1,377,025
Weighted average shares - Diluted	97,688,233	120,943,745	97,669,309	120,903,032
Net income per share attributable to common shareholders of Party City Holdco Inc. - Basic	$ 0.30	$ 0.21	$ 0.28	$ 0.17
Net income per share attributable to common shareholders of Party City Holdco Inc. - Diluted	$ 0.29	$ 0.21	$ 0.28	$ 0.17

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of call options and warrants using the treasury stock method.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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Number of shares of restricted stock determined by relating the portion of time within a reporting period that restricted shares have been outstanding to the total time in that period. Restricted shares are subject to sales, contractual, regulatory or other restrictions that prevent or inhibit the holder from freely disposing of them before the restriction ends.

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