Derivative Instruments - Schedule of Gross and Net Amount Offset (Detail) - Balance Sheet Offsetting $ in Millions	Dec. 31, 2015 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Fair Value	$ 42
Counterparty Offsetting	16
Net Fair Value in the Consolidated Balance Sheets	26
Counterparty A
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Fair Value	12
Counterparty Offsetting	6
Net Fair Value in the Consolidated Balance Sheets	6
Counterparty B
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Fair Value	4
Counterparty Offsetting	2
Net Fair Value in the Consolidated Balance Sheets	2
Counterparty C
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Fair Value	4
Counterparty Offsetting	2
Net Fair Value in the Consolidated Balance Sheets	2
Counterparty D
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Fair Value	9
Counterparty Offsetting	3
Net Fair Value in the Consolidated Balance Sheets	6
Counterparty E
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Fair Value	4
Counterparty Offsetting	1
Net Fair Value in the Consolidated Balance Sheets	3
Counterparty F
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Fair Value	4
Counterparty Offsetting	2
Net Fair Value in the Consolidated Balance Sheets	2
Counterparty G
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross Fair Value	5
Counterparty Offsetting	0
Net Fair Value in the Consolidated Balance Sheets	$ 5