Convertible and Long-Term Debt Obligations - Solar Bonds - Additional Information (Detail) $ in Millions	1 Months Ended
Apr. 30, 2017 USD ($)
Solar Bonds [Member]
Debt Instrument [Line Items]
Debt instrument prepayment of principal and interest amount	$ 20.9

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.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration