Debt - Additional Information (Detail) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
	Jan. 20, 2016	Jun. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Agreement date		Apr. 18, 2014
Minimum asset coverage ratio	150.00%
Maximum capitalization ratio	45.00%		50.00%
Base rate	0.75%
Percentage increase in commitment fee	0.05%
Percentage of equity in customary security interest	65.00%
Senior secured revolving credit facility commitment		$ 750
Percentage of borrowings in excess subject to minimum fixed charge ratio		75.00%
Accordion		$ 250
Debt		180	$ 108
Senior Secured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt		$ 180