Variable Interest Entities - Summary of VIEs (Detail) - Jun. 30, 2015	USD ($) MW
Pilesgrove | Minimum | Solar Renewable Energy Credit Hedge
Variable Interest Entity [Line Items]
Renewable Energy Credit	3 years
Pilesgrove | Maximum | Solar Renewable Energy Credit Hedge
Variable Interest Entity [Line Items]
Renewable Energy Credit	5 years
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure
Variable Interest Entity [Line Items]
Percentage of variable interests	50.00%
Variable Interest Entity, Not Primary Beneficiary | Copper Mountain Solar 3 | Nevada
Variable Interest Entity [Line Items]
Generating Capacity Owned (MWs AC) | MW	128
Power Purchase Agreement Term in Years	20 years
Year of Initial Investment	2014
Maximum exposure to loss	$ 187,000,000
Variable Interest Entity, Not Primary Beneficiary | Mesquite Solar 1 | Arizona
Variable Interest Entity [Line Items]
Generating Capacity Owned (MWs AC) | MW	83
Power Purchase Agreement Term in Years	20 years
Year of Initial Investment	2013
Maximum exposure to loss	$ 105,000,000
Variable Interest Entity, Not Primary Beneficiary | Copper Mountain Solar 2 | Nevada
Variable Interest Entity [Line Items]
Generating Capacity Owned (MWs AC) | MW	75
Power Purchase Agreement Term in Years	25 years
Year of Initial Investment	2013
Maximum exposure to loss	$ 88,000,000
Variable Interest Entity, Not Primary Beneficiary | California Solar | California
Variable Interest Entity [Line Items]
Generating Capacity Owned (MWs AC) | MW	55
Power Purchase Agreement Term in Years	25 years
Year of Initial Investment	2012
Maximum exposure to loss	$ 73,000,000
Variable Interest Entity, Not Primary Beneficiary | Broken Bow II | Nebraska
Variable Interest Entity [Line Items]
Generating Capacity Owned (MWs AC) | MW	37
Power Purchase Agreement Term in Years	25 years
Year of Initial Investment	2014
Maximum exposure to loss	$ 56,000,000
Variable Interest Entity, Not Primary Beneficiary | Pilesgrove | New Jersey
Variable Interest Entity [Line Items]
Generating Capacity Owned (MWs AC) | MW	9
Year of Initial Investment	2010
Maximum exposure to loss	$ 26,000,000
Variable Interest Entity, Primary Beneficiary | Texas Solar 4
Variable Interest Entity [Line Items]
Percentage of variable interests	80.00%
VIEs, noncontrolling interest	$ 9,000,000
Variable Interest Entity, Primary Beneficiary | Texas Solar 4 | Texas
Variable Interest Entity [Line Items]
Generating Capacity Owned (MWs AC) | MW	32
Power Purchase Agreement Term in Years	25 years
Year of Initial Investment	2014
Maximum exposure to loss	$ 49,000,000