RECONCILIATION OF PREVIOUSLY REPORTED AMOUNTS TO AMOUNTS AS RESTATED Restated Consolidated Statements of Operations and Comprehensive Income (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Sales	$ 286,453	$ 268,297	$ 265,943	$ 229,601	$ 230,456	$ 216,898	$ 214,312	$ 200,586	$ 1,050,294	$ 862,252	$ 898,496
Cost of sales		173,335	168,669	153,003	156,221	144,559	144,431	136,709	678,609	581,920	600,602
Gross profit	102,850	94,962	97,274	76,598	74,235	72,339	69,881	63,877	371,685	280,332	297,894
Selling, general, and administrative expenses		71,647	74,833	64,722	58,425	55,485	57,276	53,729	286,801	224,915	206,422
Restructuring and other charges	700		203	592	5,104		0	0	1,532	5,104	0
Intangible asset impairment charge					8,900				0	8,900	0
Operating profit		23,315	22,238	11,284	1,806	16,854	12,605	10,148	76,843	41,413	91,472
Interest expense		1,899	1,944	1,671	1,445	1,484	1,517	1,495	7,378	5,941	6,350
Other (income) expense, net		(3,294)	2,700	(2,504)	(2,157)	2,224	(2,206)	(1,291)	(6,285)	(3,430)	3,215
Income before income tax expense		24,710	17,594	12,117	2,518	13,146	13,294	9,944	75,750	38,902	81,907
Income tax expense		9,113	6,753	4,285	1,772	4,916	5,481	3,549	29,165	15,718	30,384
Net earnings	12,316	15,597	10,841	7,832	746	8,230	7,813	6,395	46,585	23,184	51,523
Net earnings per common share attributable to Knoll, Inc. stockholders:
Basic (in dollars per share)	$ 0.26	$ 0.33	$ 0.23	$ 0.17	$ 0.02	$ 0.18	$ 0.17	$ 0.14	$ 0.98	$ 0.49	$ 1.10
Diluted (in dollars per share)	$ 0.26	$ 0.33	$ 0.23	$ 0.16	$ 0.02	$ 0.17	$ 0.16	$ 0.13	$ 0.97	$ 0.49	$ 1.09
Other comprehensive income (loss):
Pension and other postretirement liability adjustment, net of tax									(25,548)	36,729	(12,358)
Foreign currency translation adjustment									(12,271)	(4,814)	1,466
Total other comprehensive income (loss), net of tax									(37,819)	31,915	(10,892)
Comprehensive income attributable to Knoll, Inc. stockholders									8,766	55,099	40,631
As previously reported
Sales		268,297	265,797	229,331	230,872	216,898	214,312	200,586		862,668	887,499
Cost of sales		173,335	168,594	152,856	156,443	144,559	144,431	136,959		582,393	593,149
Gross profit		94,962	97,203	76,475	74,429	72,339	69,881	63,627		280,275	294,350
Selling, general, and administrative expenses		71,647	74,805	64,650	58,525	55,288	57,473	53,333		224,619	206,449
Restructuring and other charges			203	0	5,696		0	0		5,696	0
Intangible asset impairment charge					8,900					8,900	0
Operating profit		23,315	22,195	11,825	1,308	17,051	12,408	10,294		41,060	87,901
Interest expense		1,899	1,944	1,671	1,445	1,484	1,517	1,495		5,941	6,350
Other (income) expense, net		(3,294)	2,700	(2,504)	(2,157)	2,224	(2,206)	(1,291)		(3,430)	3,215
Income before income tax expense		24,710	17,551	12,658	2,020	13,343	13,097	10,090		38,549	78,336
Income tax expense		9,088	6,712	4,466	1,386	4,793	5,209	4,016		15,403	28,335
Net earnings		15,622	10,839	8,192	634	8,550	7,888	6,074		23,146	50,001
Net earnings per common share attributable to Knoll, Inc. stockholders:
Basic (in dollars per share)		$ 0.33	$ 0.23	$ 0.17	$ 0.01	$ 0.18	$ 0.17	$ 0.13		$ 0.49	$ 1.07
Diluted (in dollars per share)		$ 0.33	$ 0.23	$ 0.17	$ 0.01	$ 0.18	$ 0.17	$ 0.13		$ 0.49	$ 1.06
Other comprehensive income (loss):
Pension and other postretirement liability adjustment, net of tax										36,729	(12,358)
Foreign currency translation adjustment										(5,947)	1,981
Total other comprehensive income (loss), net of tax										30,782	(10,377)
Comprehensive income attributable to Knoll, Inc. stockholders										53,928	39,624
Correction of prior period misstatements
Sales		0	146	270	(416)	0	0	0		(416)	10,997
Cost of sales		0	75	147	(222)	0	0	(250)		(473)	7,453
Gross profit		0	71	123	(194)	0	0	250		57	3,544
Selling, general, and administrative expenses		0	28	72	(100)	197	(197)	396		296	(27)
Restructuring and other charges			0	592	(592)		0	0		(592)	0
Intangible asset impairment charge					0					0	0
Operating profit		0	43	(541)	498	(197)	197	(146)		353	3,571
Interest expense		0	0	0	0	0	0	0		0	0
Other (income) expense, net		0	0	0	0	0	0	0		0	0
Income before income tax expense		0	43	(541)	498	(197)	197	(146)		353	3,571
Income tax expense		25	41	(181)	386	123	272	(467)		315	2,049
Net earnings		(25)	2	(360)	112	(320)	(75)	321		38	1,522
Net earnings per common share attributable to Knoll, Inc. stockholders:
Basic (in dollars per share)		$ 0.00	$ 0.00	$ 0.00	$ 0.01	$ 0.00	$ 0.00	$ 0.01		$ 0.00	$ 0.03
Diluted (in dollars per share)		$ 0.00	$ 0.00	$ (0.01)	$ 0.01	$ (0.01)	$ (0.01)	$ 0.00		$ 0.00	$ 0.03
Other comprehensive income (loss):
Pension and other postretirement liability adjustment, net of tax										0	0
Foreign currency translation adjustment										1,133	(515)
Total other comprehensive income (loss), net of tax										1,133	(515)
Comprehensive income attributable to Knoll, Inc. stockholders										$ 1,171	$ 1,007