Supplemental Guarantor Information Supplemental Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Home sales	$ 279,885	$ 114,622	$ 96,929	$ 69,406	$ 261,668	$ 125,142	$ 78,836	$ 42,303	$ 560,842	$ 507,949	$ 280,209
Fee building, including management fees from unconsolidated joint ventures of $4,945, $8,202 and $12,426, respectively	44,217	43,309	47,181	55,617	60,781	52,761	30,028	42,937	190,324	186,507	149,890
Revenue, Net									751,166	694,456	430,099
Home sales	234,668	95,992	82,488	60,065	221,700	105,799	69,390	36,670	473,213	433,559	235,232
Home sales impairments	900	0	1,300	0	2,350	0	0	0	2,200	2,350	0
Impairment of Real Estate Land					1,150	0	0	0	0	1,150	0
Fee building	43,194	41,808	45,899	53,926	58,040	50,832	28,317	40,914	184,827	178,103	139,677
Cost of Sales									660,240	615,162	374,909
Gross Profit Home Sales	44,317	18,630	13,141	9,341	37,618	19,343	9,446	5,633	85,429	72,040	44,977
Gross Profit Fee Building	1,023	1,501	1,282	1,691	2,741	1,929	1,711	2,023	5,497	8,404	10,213
Gross Profit Land Sales					(1,150)	0	0	0	0	(1,150)	0
Gross Profit									90,926	79,294	55,190
Selling and marketing expenses									(32,702)	(26,744)	(13,741)
General and administrative expenses									(26,330)	(25,882)	(20,278)
Equity in net income of unconsolidated joint ventures									866	7,691	13,767
Equity in net income (loss) of subsdiaries									0	0	0
Other income (expense), net									(229)	(409)	(1,027)
Pretax income	21,692	6,974	2,505	1,360	22,080	9,042	3,939	(1,111)	32,531	33,950	33,911
Provision for income taxes									(15,390)	(13,024)	(12,533)
Net income									17,141	20,926	21,378
Net loss attributable to noncontrolling interest									11	96	310
Net income attributable to The New Home Company Inc.	$ 10,471	$ 4,318	$ 1,517	$ 846	$ 13,780	$ 5,547	$ 2,509	$ (814)	17,152	21,022	21,688
Guarantor Subsidiaries [Member]
Home sales									560,842	502,792	269,225
Fee building, including management fees from unconsolidated joint ventures of $4,945, $8,202 and $12,426, respectively									190,324	186,662	150,220
Revenue, Net									751,166	689,454	419,445
Home sales									473,181	428,881	225,379
Home sales impairments									2,200	2,350
Impairment of Real Estate Land										1,150
Fee building									184,827	175,863	137,942
Cost of Sales									660,208	608,244	363,321
Gross Profit Home Sales									85,461	71,561	43,846
Gross Profit Fee Building									5,497	10,799	12,278
Gross Profit Land Sales										(1,150)
Gross Profit									90,958	81,210	56,124
Selling and marketing expenses									(32,702)	(26,058)	(12,378)
General and administrative expenses									(23,927)	(11,163)	(6,676)
Equity in net income of unconsolidated joint ventures									866	7,691	13,767
Equity in net income (loss) of subsdiaries									0	0	0
Other income (expense), net									(336)	(303)	(414)
Pretax income									34,859	51,377	50,423
Provision for income taxes									13,065	19,033	18,436
Net income									21,794	32,344	31,987
Net loss attributable to noncontrolling interest									0	0	0
Net income attributable to The New Home Company Inc.									21,794	32,344	31,987
Non-Guarantor Subsidiaries [Member]
Home sales									0	5,157	10,984
Fee building, including management fees from unconsolidated joint ventures of $4,945, $8,202 and $12,426, respectively									0	0	0
Revenue, Net									0	5,157	10,984
Home sales									32	4,678	9,853
Home sales impairments									0	0
Impairment of Real Estate Land										0
Fee building									0	0	0
Cost of Sales									32	4,678	9,853
Gross Profit Home Sales									(32)	479	1,131
Gross Profit Fee Building									0	0	0
Gross Profit Land Sales										0
Gross Profit									(32)	479	1,131
Selling and marketing expenses									0	(686)	(1,363)
General and administrative expenses									0	0	0
Equity in net income of unconsolidated joint ventures									0	0	0
Equity in net income (loss) of subsdiaries									0	0	0
Other income (expense), net									0	(142)	(642)
Pretax income									(32)	(349)	(874)
Provision for income taxes									0	0	0
Net income									(32)	(349)	(874)
Net loss attributable to noncontrolling interest									11	96	310
Net income attributable to The New Home Company Inc.									(21)	(253)	(564)
Parent Company [Member]
Home sales									0	0	0
Fee building, including management fees from unconsolidated joint ventures of $4,945, $8,202 and $12,426, respectively									0	0	0
Revenue, Net									0	0	0
Home sales									0	0	0
Home sales impairments									0	0
Impairment of Real Estate Land										0
Fee building									0	2,240	1,735
Cost of Sales									0	2,240	1,735
Gross Profit Home Sales									0	0	0
Gross Profit Fee Building									0	(2,240)	(1,735)
Gross Profit Land Sales										0
Gross Profit									0	(2,240)	(1,735)
Selling and marketing expenses									0	0	0
General and administrative expenses									(2,403)	(14,719)	(13,602)
Equity in net income of unconsolidated joint ventures									0	0	0
Equity in net income (loss) of subsdiaries									21,773	32,091	31,423
Other income (expense), net									107	(119)	(301)
Pretax income									19,477	15,013	15,785
Provision for income taxes									2,325	(6,009)	(5,903)
Net income									17,152	21,022	21,688
Net loss attributable to noncontrolling interest									0	0	0
Net income attributable to The New Home Company Inc.									17,152	21,022	21,688
Consolidation, Eliminations [Member]
Home sales									0	0	0
Fee building, including management fees from unconsolidated joint ventures of $4,945, $8,202 and $12,426, respectively									0	(155)	(330)
Revenue, Net									0	(155)	(330)
Home sales									0	0	0
Home sales impairments									0	0
Impairment of Real Estate Land										0
Fee building									0	0	0
Cost of Sales									0	0	0
Gross Profit Home Sales									0	0	0
Gross Profit Fee Building									0	(155)	(330)
Gross Profit Land Sales										0
Gross Profit									0	(155)	(330)
Selling and marketing expenses									0	0	0
General and administrative expenses									0	0	0
Equity in net income of unconsolidated joint ventures									0	0	0
Equity in net income (loss) of subsdiaries									(21,773)	(32,091)	(31,423)
Other income (expense), net									0	155	330
Pretax income									(21,773)	(32,091)	(31,423)
Provision for income taxes									0	0	0
Net income									(21,773)	(32,091)	(31,423)
Net loss attributable to noncontrolling interest									0	0	0
Net income attributable to The New Home Company Inc.									$ (21,773)	$ (32,091)	$ (31,423)