Stock Based Compensation and Employee Benefit Plans - Additional Information (Detail) In Thousands, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended			1 Months Ended		1 Months Ended		3 Months Ended	0 Months Ended	3 Months Ended		0 Months Ended
	Apr. 16, 2014	Mar. 31, 2015 USD ($)	Mar. 31, 2014	Apr. 16, 2014 USD ($)	Apr. 30, 2014 2013 Wind Power Holdings Inc Plan [Member]	Mar. 31, 2015 2013 Wind Power Holdings Inc Plan [Member] Subsidiary	Jan. 31, 2014 2013 Wind Power Holdings Inc Plan [Member] Mira III [Member]	Jan. 31, 2014 2013 Wind Power Holdings Inc Plan [Member] Northern Power Systems Utility Scale, Inc [Member]	Mar. 31, 2015 2014 NPS Corp Plan [Member] USD ($)	Apr. 16, 2014 Mira III Stock Option Awards [Member]	Mar. 31, 2015 Mira III Stock Option Awards [Member] CAD	Apr. 16, 2014 Mira III Stock Option Awards [Member] CAD	Jan. 01, 2014 Subsidiary Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Number of operating subsidiaries						2
Outstanding options converted							1,938,094	2,088,842					238,887
Common stock reserved for future issuance		2,568,089							4,000,000
Outstanding options converted					1,830,012
Weighted-average grant-date fair value of options granted		$ 1.09
Unrecognized compensation expense related to non-vested stock options		$ 1,602
Expected weighted-average vesting period to recognize stock compensation expenses		2 years 1 month 6 days
Shares reserved for issuance upon grant or exercise									1,591,739		0
Stock option activity, forfeiture rate		10.00%	10.00%
Number of exercisable option shares sold in offering				367,500					1,123,569		35,938	35,938
Exercise option price per share				$ 3.64					$ 2.18		3.48	3.48
Stock option expected term	2 years	4 years 6 months								1 year
Shares, Exercised									1,596		7,187
Common shares exercise price during the period									$ 1.59		3.48