Variable Interest Entities - Summary of VIEs (Detail)		1 Months Ended	9 Months Ended
	Sep. 30, 2015 USD ($) MW	Sep. 30, 2015 USD ($)	Sep. 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, Aggregated Disclosure | Panoche Valley
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 (MWs AC) | MW			128
Power Purchase Agreement Term in Years			20 years
Year of Initial Investment			2014
Maximum exposure to loss	$ 189,000,000	$ 189,000,000	$ 189,000,000
Variable Interest Entity, Not Primary Beneficiary | Mesquite Solar 1 | Arizona
Variable Interest Entity [Line Items]
Generating Capacity (MWs AC) | MW			83
Power Purchase Agreement Term in Years			20 years
Year of Initial Investment			2013
Maximum exposure to loss	108,000,000	108,000,000	$ 108,000,000
Variable Interest Entity, Not Primary Beneficiary | Copper Mountain Solar 2 | Nevada
Variable Interest Entity [Line Items]
Generating Capacity (MWs AC) | MW			75
Power Purchase Agreement Term in Years			25 years
Year of Initial Investment			2013
Maximum exposure to loss	85,000,000	85,000,000	$ 85,000,000
Variable Interest Entity, Not Primary Beneficiary | California Solar | California
Variable Interest Entity [Line Items]
Generating Capacity (MWs AC) | MW			55
Power Purchase Agreement Term in Years			25 years
Year of Initial Investment			2012
Maximum exposure to loss	$ 76,000,000	76,000,000	$ 76,000,000
Variable Interest Entity, Not Primary Beneficiary | Panoche Valley | California
Variable Interest Entity [Line Items]
Generating Capacity (MWs AC) | MW	247		124
Power Purchase Agreement Term in Years			20 years
Year of Initial Investment			2015
Maximum exposure to loss	$ 58,000,000	58,000,000	$ 58,000,000
Variable Interest Entity, Not Primary Beneficiary | Broken Bow II | Nebraska
Variable Interest Entity [Line Items]
Generating Capacity (MWs AC) | MW			37
Power Purchase Agreement Term in Years			25 years
Year of Initial Investment			2014
Maximum exposure to loss	55,000,000	55,000,000	$ 55,000,000
Variable Interest Entity, Not Primary Beneficiary | Pilesgrove | New Jersey
Variable Interest Entity [Line Items]
Generating Capacity (MWs AC) | MW			9
Year of Initial Investment			2010
Maximum exposure to loss	26,000,000	26,000,000	$ 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	9,000,000	$ 9,000,000
Variable Interest Entity, Primary Beneficiary | Texas Solar 4 | Texas
Variable Interest Entity [Line Items]
Generating Capacity (MWs AC) | MW			32
Power Purchase Agreement Term in Years			25 years
Year of Initial Investment			2014
Maximum exposure to loss	$ 49,000,000	$ 49,000,000	$ 49,000,000