Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Details)

v3.3.1.900
Summary of Significant Accounting Policies - Additional Information (Details)
12 Months Ended
Dec. 31, 2015
USD ($)
$ / participant
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Accounting Policies [Abstract]      
Maximum exposure, per participant | $ / participant 100,000    
Restricted cash, noncurrent $ 13,515,000 $ 16,165,000  
Interest costs capitalized 941,000 518,000 $ 1,825,000
Proceeds from Section 1603 grants 0 3,727,000 $ 3,262,000
Deferred grant income 8,291,000 8,842,000  
Rebates from utility company 0 $ 0  
Carrying value of fixed-rate long-term debt in excess of fair value $ 1,175,000