Segment Information (Summary Of Financial Information In Reportable Segments) (Details) (USD $) In Thousands, 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
Segment Reporting Information [Line Items]
Revenues	$ 81,747	$ 65,044	$ 57,069	$ 52,797	$ 73,580	$ 81,510	$ 70,187	$ 44,957	$ 256,657	$ 270,234	$ 162,039
Cost of Sales (excluding depreciation and amortization)									192,088	198,651	110,953
Gross Profit	21,126	18,071	14,331	11,041	16,510	21,450	19,883	13,740	64,569	71,583	51,086
General and administrative									56,419	47,071	36,201
Selling, marketing and service									8,890	7,381	5,560
Depreciation and amortization									8,902	7,287	4,780
Restructuring charges									427	1,205	2,675
Total operating expenses	20,110	18,597	18,273	17,658	18,337	15,509	16,425	12,673	74,638	62,944	49,216
Operating income (loss)	1,016	(526)	(3,942)	(6,617)	(1,827)	5,941	3,458	1,067	(10,069)	8,639	1,870
Gain on sale of unconsolidated affiliate											1,439
Interest and other income	(114)	(324)	(287)	(296)	(300)	(241)	(111)	(84)	215	81	88
Interest expense									(1,236)	(817)	(449)
Income (loss) before income taxes									(11,090)	7,903	2,948
Total capital expenditures									12,831	9,622
Total goodwill	40,210				30,226				40,210	30,226	12,884
Total assets	265,217				255,491				265,217	255,491
Eliminations And Other [Member]
Segment Reporting Information [Line Items]
Revenues									(602)
Cost of Sales (excluding depreciation and amortization)									(602)
General and administrative									19,187	12,763	13,044
Selling, marketing and service									1,008	134	2,206
Depreciation and amortization									662	532	434
Restructuring charges											820
Total operating expenses									20,857	13,429	16,504
Operating income (loss)									(20,857)	(13,429)	(16,504)
Gain on sale of unconsolidated affiliate											1,439
Interest and other income									215	81	88
Interest expense									(1,236)	(817)	(449)
Income (loss) before income taxes									(21,878)	(14,165)	(15,426)
Total capital expenditures									2,021	755
Total assets	51,808				66,904				51,808	66,904
Distributed Generation [Member]
Segment Reporting Information [Line Items]
Revenues									100,017	111,536	76,352
Cost of Sales (excluding depreciation and amortization)									68,648	70,354	46,951
Gross Profit									31,369	41,182	29,401
General and administrative									15,434	13,733	11,717
Selling, marketing and service									4,240	4,293	1,956
Depreciation and amortization									3,437	2,760	2,476
Restructuring charges											1,267
Total operating expenses									23,111	20,786	17,416
Operating income (loss)									8,258	20,396	11,985
Income (loss) before income taxes									8,258	20,396	11,985
Total capital expenditures									7,479	5,629
Total goodwill	16,317				6,939				16,317	6,939
Total assets	113,056				88,360				113,056	88,360
Utility Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									103,204	111,654	60,735
Cost of Sales (excluding depreciation and amortization)									88,199	89,908	45,703
Gross Profit									15,005	21,746	15,032
General and administrative									11,255	10,901	7,855
Selling, marketing and service									1,445	1,585	372
Depreciation and amortization									3,446	2,658	1,478
Restructuring charges											152
Total operating expenses									16,146	15,144	9,857
Operating income (loss)									(1,141)	6,602	5,175
Income (loss) before income taxes									(1,141)	6,602	5,175
Total capital expenditures									2,564	2,838
Total goodwill	2,325				2,325				2,325	2,325
Total assets	55,660				48,709				55,660	48,709
Energy Efficiency [Member]
Segment Reporting Information [Line Items]
Revenues									54,038	47,044	24,952
Cost of Sales (excluding depreciation and amortization)									35,843	38,389	18,299
Gross Profit									18,195	8,655	6,653
General and administrative									10,543	9,674	3,585
Selling, marketing and service									2,197	1,369	1,026
Depreciation and amortization									1,357	1,337	392
Restructuring charges									427	1,205	436
Total operating expenses									14,524	13,585	5,439
Operating income (loss)									3,671	(4,930)	1,214
Income (loss) before income taxes									3,671	(4,930)	1,214
Total capital expenditures									767	400
Total goodwill	21,568				20,962				21,568	20,962
Total assets	$ 44,693				$ 51,518				$ 44,693	$ 51,518