Segment Information (Summary Of Financial Information In Reportable Segments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 107,182	$ 57,069	$ 186,691	$ 109,866
Cost of Sales (excluding depreciation and amortization)	83,111	42,738	141,291	84,494
Gross Profit	24,071	14,331	45,400	25,372
General and administrative	16,705	13,670	32,339	26,714
Selling, marketing and service	2,973	2,466	5,721	4,475
Depreciation and amortization	$ 2,612	2,137	5,089	4,315
Restructuring charges				427
Total operating expenses	$ 22,290	18,273	43,149	35,931
Operating income (loss)	1,781	(3,942)	2,251	(10,559)
Interest and other income	2	5	3	9
Interest expense	(287)	(292)	(556)	(592)
Income (loss) before income taxes	1,496	(4,229)	1,698	(11,142)
Total capital expenditures YTD 2015			6,569
Total goodwill	40,210		40,210		$ 40,210
Total assets	269,680		269,680		$ 265,217
Eliminations And Other [Member]
Segment Reporting Information [Line Items]
Revenues	(190)	(421)	(205)	(421)
Cost of Sales (excluding depreciation and amortization)	(190)	(421)	(205)	(421)
General and administrative	4,896	5,048	9,263	9,561
Selling, marketing and service	290	351	800	421
Depreciation and amortization	306	160	513	317
Total operating expenses	5,492	5,559	10,576	10,299
Operating income (loss)	(5,492)	(5,559)	(10,576)	(10,299)
Interest and other income	2	5	3	9
Interest expense	(287)	(292)	(556)	(592)
Income (loss) before income taxes	(5,777)	(5,846)	(11,129)	(10,882)
Total capital expenditures YTD 2015			780
Total assets	37,224		37,224
Distributed Generation [Member]
Segment Reporting Information [Line Items]
Revenues	34,263	20,205	64,994	37,195
Cost of Sales (excluding depreciation and amortization)	22,530	13,195	41,411	23,822
Gross Profit	11,733	7,010	23,583	13,373
General and administrative	4,723	2,886	9,083	5,916
Selling, marketing and service	1,423	985	2,637	2,036
Depreciation and amortization	1,079	781	2,149	1,559
Total operating expenses	7,225	4,652	13,869	9,511
Operating income (loss)	4,508	2,358	9,714	3,862
Income (loss) before income taxes	4,508	2,358	9,714	3,862
Total capital expenditures YTD 2015			3,223
Total goodwill	11,403		11,403
Total assets	115,325		115,325
Solar Energy [Member]
Segment Reporting Information [Line Items]
Revenues	24,985	2,108	31,333	2,613
Cost of Sales (excluding depreciation and amortization)	22,695	1,885	28,428	2,424
Gross Profit	2,290	223	2,905	189
General and administrative	940	470	1,719	977
Selling, marketing and service	196	112	293	225
Depreciation and amortization	32	24	64	48
Total operating expenses	1,168	606	2,076	1,250
Operating income (loss)	1,122	(383)	829	(1,061)
Income (loss) before income taxes	1,122	(383)	829	(1,061)
Total capital expenditures YTD 2015			268
Total goodwill	4,914		4,914
Total assets	16,408		16,408
Utility Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues	33,264	23,770	62,147	50,598
Cost of Sales (excluding depreciation and amortization)	28,229	20,257	53,262	44,424
Gross Profit	5,035	3,513	8,885	6,174
General and administrative	3,347	2,626	6,220	5,549
Selling, marketing and service	361	318	697	622
Depreciation and amortization	830	867	1,606	1,726
Total operating expenses	4,538	3,811	8,523	7,897
Operating income (loss)	497	(298)	362	(1,723)
Income (loss) before income taxes	497	(298)	362	(1,723)
Total capital expenditures YTD 2015			1,918
Total goodwill	2,325		2,325
Total assets	54,979		54,979
Energy Efficiency [Member]
Segment Reporting Information [Line Items]
Revenues	14,860	11,407	28,422	19,881
Cost of Sales (excluding depreciation and amortization)	9,847	7,822	18,395	14,245
Gross Profit	5,013	3,585	10,027	5,636
General and administrative	2,799	2,640	6,054	4,711
Selling, marketing and service	703	700	1,294	1,171
Depreciation and amortization	365	305	757	665
Restructuring charges				427
Total operating expenses	3,867	3,645	8,105	6,974
Operating income (loss)	1,146	(60)	1,922	(1,338)
Income (loss) before income taxes	1,146	$ (60)	1,922	$ (1,338)
Total capital expenditures YTD 2015			380
Total goodwill	21,568		21,568
Total assets	$ 45,744		$ 45,744