Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Outstanding Loans and Security Agreements - Schedule of Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 18, 2018	Dec. 31, 2017	Jul. 01, 2017	Jun. 30, 2017	Dec. 31, 2014	Jul. 31, 2014	Mar. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Unpaid principal balance	$ 1,016,277		$ 1,008,104
Current portion of debt	30,006		20,136
Long-term portion of debt	930,123		921,205
Total	960,129		941,341
Unused Borrowing Capacity	$ 1,504		$ 1,784
Interest rate percentage			8.00%
Notes due July 2024, Recourse
Debt Instrument [Line Items]
Interest rate percentage	10.00%		10.00%
Term loan \| Term Loan due November 2020, Recourse
Debt Instrument [Line Items]
Unpaid principal balance	$ 4,050		$ 5,000
Current portion of debt	1,688		1,690
Long-term portion of debt	2,362		3,197
Total	4,050		4,887
Non-recourse debt
Debt Instrument [Line Items]
Unpaid principal balance	363,348		372,318
Current portion of debt	19,655		18,446
Long-term portion of debt	333,102		342,050
Total	352,757		360,496
Convertible promissory notes \| Convertible Promissory Notes due December 2019 and 2020, Recourse
Debt Instrument [Line Items]
Unpaid principal balance	254,120		244,717
Current portion of debt	8,663		0
Long-term portion of debt	245,457		244,717
Total	$ 254,120		$ 244,717
Interest rate percentage	5.00%	5.00%	8.00%			8.00%
Convertible promissory notes \| Convertible Promissory Notes due December 2020, Recourse
Debt Instrument [Line Items]
Unpaid principal balance	$ 294,759		$ 286,069
Current portion of debt	0		0
Long-term portion of debt	254,062		236,724
Total	$ 254,062		236,724
Interest rate percentage	6.00%			6.00%	5.00%
Notes \| Notes due July 2024, Recourse
Debt Instrument [Line Items]
Unpaid principal balance	$ 100,000		100,000
Current portion of debt	0		0
Long-term portion of debt	95,140		94,517
Total	95,140		94,517
Interest rate percentage					10.00%
Recourse debt
Debt Instrument [Line Items]
Unpaid principal balance	652,929		635,786
Current portion of debt	10,351		1,690
Long-term portion of debt	597,021		579,155
Total	607,372		580,845
PPA Company II \| Senior secured notes \| Senior Secured Notes due March 2025, Non-Recourse
Debt Instrument [Line Items]
Unpaid principal balance	85,513		91,086
Current portion of debt	11,687		11,389
Long-term portion of debt	72,504		78,175
Total	$ 84,191		$ 89,564
Interest rate percentage	5.20%		5.20%					5.22%
PPA Company IIIa \| Term loan \| Term Loan due September 2028, Non-Recourse
Debt Instrument [Line Items]
Unpaid principal balance	$ 41,301		$ 41,927
Current portion of debt	1,630		1,389
Long-term portion of debt	35,054		35,551
Total	$ 36,684		$ 36,940
Interest rate percentage	7.50%		7.50%						7.50%
PPA Company IIIb \| Term loan \| Senior Secured Notes due October 2020, Non-Recourse
Debt Instrument [Line Items]
Unpaid principal balance	$ 25,153		$ 25,599
Current portion of debt	890		876
Long-term portion of debt	23,243		23,488
Total	24,133		24,364
PPA Company IV \| Senior secured notes \| Senior Secured Notes due March 2030, Non-Recourse
Debt Instrument [Line Items]
Unpaid principal balance	84,418		85,303
Current portion of debt	2,150		1,846
Long-term portion of debt	81,073		82,186
Total	$ 83,223		$ 84,032
Interest rate percentage	6.10%		6.10%				6.07%
PPA Company V \| Term loan \| Term Loan due December 2021, Non-Recourse
Debt Instrument [Line Items]
Unpaid principal balance	$ 126,963		$ 128,403
Current portion of debt	3,298		2,946
Long-term portion of debt	121,228		122,650
Total	$ 124,526		$ 125,596
PPA Company V \| Letters of Credit
Debt Instrument [Line Items]
Interest rate percentage	2.25%		2.25%
Letters of Credit
Debt Instrument [Line Items]
Unused Borrowing Capacity	$ 1,504		$ 1,784
Letters of Credit \| PPA Company V
Debt Instrument [Line Items]
Unused Borrowing Capacity	$ 1,504		$ 1,784