Power Purchase Agreement Programs - Schedule of PPA Entities' Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 220,728	$ 103,828
Restricted cash, current	28,657	44,387
Accounts receivable	84,887	30,317
Customer financing receivable	5,594	5,209
Total current assets	672,581	419,981
Property, plant and equipment, net	481,414	497,789
Non-current portion of investment in sales-type financing leases	67,082	72,677
Restricted cash, non-current	31,100	32,397
Other long-term assets	34,792	37,460
Total assets	1,389,668	1,220,987
Current liabilities:
Accounts payable	66,889	48,582
Accrued other current liabilities	69,535	67,649
Deferred revenue and customer deposits	94,158	118,106
Current portion of debt	29,848	20,136
Total current liabilities	279,666	271,284
Derivative liabilities	10,128	156,552
Deferred revenue and customer deposits	241,794	309,843
Long-term portion of debt	711,433	921,205
Other long-term liabilities	55,937	52,915
Total liabilities	1,298,958	1,721,624
Variable Interest Entity, Primary Beneficiary
Current assets:
Cash and cash equivalents	5,295	9,549
Restricted cash, current	2,917	7,969
Accounts receivable	7,516	7,680
Customer financing receivable	5,594	5,209
Prepaid expenses and other current assets	4,909	6,365
Total current assets	26,231	36,772
Property, plant and equipment, net	399,060	430,464
Non-current portion of investment in sales-type financing leases	67,082	72,677
Restricted cash, non-current	27,854	26,748
Other long-term assets	2,692	3,767
Total assets	522,919	570,428
Current liabilities:
Accounts payable	724	520
Accrued other current liabilities	1,442	2,378
Deferred revenue and customer deposits	786	786
Current portion of debt	21,162	18,446
Total current liabilities	24,114	22,130
Derivative liabilities	3,626	5,060
Deferred revenue and customer deposits	8,696	9,482
Long-term portion of debt	323,360	342,050
Other long-term liabilities	1,798	1,226
Total liabilities	$ 361,594	$ 379,948