CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Total Sales	$ 327,737	$ 291,256	$ 947,647	$ 816,770
Cost of sales	204,943	184,646	597,855	514,528
Gross profit	122,794	106,610	349,792	302,242
Selling, general, and administrative expenses	88,674	78,883	267,036	231,897
Restructuring charges	1,200	0	2,564	2,150
Operating profit	32,920	27,727	80,192	68,195
Pension settlement charge	628	0	5,236	0
Interest expense	5,032	1,991	15,812	5,521
Other income, net	(227)	(1,583)	(7,021)	(5,943)
Income before income tax expense	27,487	27,319	66,165	68,617
Income tax expense	7,164	8,158	17,452	21,104
Net earnings	20,323	19,161	48,713	47,513
Net earnings attributable to noncontrolling interests	0	29	7	43
Net earnings attributable to Knoll, Inc. stockholders	$ 20,323	$ 19,132	$ 48,706	$ 47,470
Net earnings per common share attributable to Knoll, Inc. stockholders:
Basic (in dollars per share)	$ 0.42	$ 0.39	$ 1.00	$ 0.98
Diluted (in dollars per share)	0.41	0.39	0.99	0.96
Dividends per share (in dollars per share)	$ 0.15	$ 0.15	$ 0.45	$ 0.45
Weighted-average number of common shares outstanding:
Basic (in shares)	48,694,438	48,468,480	48,641,595	48,406,659
Diluted (in shares)	49,231,376	48,979,182	49,189,592	49,167,856
Other comprehensive income (loss) :
Unrealized gain on interest rate swap, net of tax	$ 911	$ 0	$ 1,964	$ 0
Pension and other post-employment liability adjustment, net of tax	1,182	(139)	9,062	(414)
Foreign currency translation adjustment	(4,649)	5,876	(10,949)	8,676
Foreign currency translation adjustment on long term intercompany notes	3,094	0	(2,498)	0
Total other comprehensive income (loss), net of tax	538	5,737	(2,421)	8,262
Total comprehensive income	20,861	24,898	46,292	55,775
Comprehensive income attributable to noncontrolling interests	0	29	7	43
Comprehensive income attributable to Knoll, Inc. stockholders	$ 20,861	$ 24,869	$ 46,285	$ 55,732