Employees Pension and Postretirement Benefits - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Deferred Compensation Plan [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
Deferred compensation plan description			The Company maintained a nonqualified deferred compensation benefit plan (the “Retirement Plan”) covering the former CEO of IMAX Entertainment and Senior Executive Vice President of the Company. Under the terms of the Retirement Plan, the benefits were due to vest in full if the executive incurred a separation from service from the Company (as defined therein).
Deferred Compensation Plan [Member] | Accrued and Other Liabilities [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
Benefit obligation recorded	$ 3,600,000		$ 3,600,000		$ 3,600,000
Deferred Compensation Plan [Member] | Prepaid Expenses [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
Company-owned life insurance	3,100,000		3,100,000		3,200,000
Richard L. Gelfond [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
Lump sump payment			$ 20,300,000
SERP Benefits [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
SERP assumptions			The accounting for the SERP assumes that Mr. Gelfond will receive a lump sum payment of $20.3 million six months after retirement at the end of the current term of his employment agreement (December 31, 2022), although Mr. Gelfond has not informed the Company that he intends to retire at that time.
Benefit Obligation	19,124,000		$ 19,124,000		18,840,000	$ 17,977,000
Interest costs	100,000	$ 100,000	284,000	$ 400,000	564,000
Expected interest costs in the remainder of the year	100,000		100,000
Companies contribution and expenses during the remainder of 2020	0		$ 0
Defined Contribution Plan [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
Defined contribution pension plans for employees			The Company also maintains defined contribution plans for its employees, including its executive officers. The Company makes contributions to these plans on behalf of employees in an amount up to 5% of their base salary subject to certain prescribed maximums.
Maximum percentage of base salary contributed to Defined Contribution Pension Plan by Company			5.00%
Canadian Plan [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
Contribution and recorded expense	300,000	300,000	$ 800,000	900,000
Us Internal Revenue Code [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
Contribution and recorded expense	100,000	100,000	500,000	500,000
Postretirement Benefits Executives [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
Benefit Obligation	600,000		600,000		700,000
Postretirement Benefits Executives [Member] | Maximum [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
Maximum amount of Postretirement benefit recorded expense	100,000	100,000	100,000	100,000
Postretirement Benefits Canadian Employees [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
Benefit Obligation	1,500,000		1,500,000		$ 1,600,000
Postretirement Benefits Canadian Employees [Member] | Maximum [Member]
Pension and Other Postretirement Benefit Expense (Textual) [Abstract]
Maximum amount of Postretirement benefit recorded expense	$ 100,000	$ 100,000	$ 100,000	$ 100,000