Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Additional Information (Detail)

v3.5.0.2
Fair Value Measurements - Additional Information (Detail) - USD ($)
$ in Millions
9 Months Ended
Sep. 30, 2016
Dec. 31, 2015
Wind Projects [Member]    
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]    
Senior secured debt investment   $ 13.0
Recognized gain on sale of debt investment $ 0.8  
Wind Projects [Member] | Large Financial Institution [Member]    
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]    
Senior secured debt investment   $ 45.0
Level 3 [Member]    
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]    
Fair value interest rate spreads, minimum 1.00%  
Fair value interest rate spreads, maximum 5.00%