Concentration of Customers - Schedule of Revenues from Customers (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Concentration Risk [Line Items]
Revenues	$ 248,186	$ 194,255	$ 439,788	$ 370,365
Sales Revenues [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Revenues	$ 248,186	$ 194,255	$ 439,788	$ 370,365
Percentage of Total	100.00%	100.00%	100.00%	100.00%
Sales Revenues [Member] | GE [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Revenues	$ 102,408	$ 98,143	$ 187,318	$ 194,294
Percentage of Total	41.30%	50.50%	42.60%	52.50%
Sales Revenues [Member] | Vestas [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Revenues	$ 82,109	$ 40,475	$ 126,431	$ 70,416
Percentage of Total	33.10%	20.80%	28.80%	19.00%
Sales Revenues [Member] | Nordex Group [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Revenues	$ 38,973	$ 35,343	$ 72,532	$ 65,007
Percentage of Total	15.70%	18.20%	16.50%	17.50%
Sales Revenues [Member] | Gamesa [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Revenues	$ 21,323	$ 18,572	$ 47,585	$ 36,709
Percentage of Total	8.60%	9.60%	10.80%	9.90%
Sales Revenues [Member] | Other [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Revenues	$ 3,373	$ 1,722	$ 5,922	$ 3,939
Percentage of Total	1.30%	0.90%	1.30%	1.10%