Summary of significant accounting policies - Additional Information (Details)	1 Months Ended	3 Months Ended									6 Months Ended	12 Months Ended
	Feb. 28, 2019 store	Mar. 31, 2020 USD ($) distribution_channel	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2016 USD ($)	Mar. 31, 2020 USD ($) segment distribution_channel	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)	Jan. 01, 2018 USD ($)	Mar. 31, 2017 customer
Summary Of Significant Accounting Policies [Line Items]
Allowance for doubtful accounts		$ 1,000,000				$ 300,000	$ 300,000					$ 1,000,000	$ 300,000
Sales allowances		7,600,000				6,500,000	7,800,000					7,600,000	7,800,000
Reserve for excess and obsolete inventory		1,400,000				1,700,000	2,300,000					1,400,000	2,300,000
Property and equipment, net		17,171,000				16,006,000	21,804,000					$ 17,171,000	21,804,000
Impairment charges											$ 0			$ 200,000
Number of operating segments | segment												1
Number of reporting segments | segment												1
Retained earnings		511,531,000				529,415,000	511,501,000					$ 511,531,000	511,501,000
Net sales		74,712,000	$ 80,760,000	$ 67,615,000	$ 59,764,000	66,141,000	78,571,000	$ 63,889,000	$ 59,055,000	$ 65,920,000		282,851,000	267,435,000	269,888,000
Accounts receivable, net		$ 29,721,000				32,275,000	36,724,000					$ 29,721,000	36,724,000
Number of distribution channels | distribution_channel		2										2
Cost of sales						25,650,000				$ 25,712,000		$ 101,728,000	104,694,000	105,163,000
Advertising costs						2,600,000						$ 26,000,000	10,200,000	8,100,000
Payment terms												The Company extends credit to retail customers based upon an evaluation of their credit quality. The majority of retail customers obtain payment terms between 30-60 days, and a contract asset is recognized for the related accounts receivable.
Operating lease, right-of-use asset		$ 13,668,000				4,445,000						$ 13,668,000
Operating lease, liability			$ 14,322,000
Number of stores closed | store	22
Retail Product Displays
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, net		$ 10,100,000				12,100,000	10,900,000					$ 10,100,000	10,900,000
Estimated useful lives												3 years
Amortization expense						1,500,000						$ 6,000,000	3,100,000	600,000
Leasehold improvements
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives												5 years
Minimum
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangibles, estimated useful life												3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangibles, estimated useful life												10 years
Revenue
Summary Of Significant Accounting Policies [Line Items]
Number of customers | customer																	2
Shipping and Handling
Summary Of Significant Accounting Policies [Line Items]
Net sales						200,000						$ 700,000	500,000	700,000
Cost of sales						$ 4,900,000						$ 19,800,000	20,900,000	$ 21,200,000
Accounting Standards Update 2016-02
Summary Of Significant Accounting Policies [Line Items]
Operating lease, right-of-use asset															$ 21,200,000
Operating lease, liability															$ 23,500,000
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Summary Of Significant Accounting Policies [Line Items]
Retained earnings																$ 100,000
Net sales													300,000
Accounts receivable, net							$ 400,000						$ 400,000