Service Agreements and Related Party Transactions - Additional Information (Detail) $ / shares in Units, $ in Thousands		9 Months Ended		12 Months Ended
	Oct. 14, 2014 Directors	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Related Party Transaction [Line Items]
Payment of stock offering fee			$ 19,310
WMMRC [Member]
Related Party Transaction [Line Items]
Administrative services agreement fee		$ 110
Pro Rata Share of the Common Stock Allotment | shares		10,000,000
Percentage of Pro Rata Share of the Common Stock Election		5.00%
Percentage of interest in litigation proceeds		50.00%
Lawsuit against number of former directors | Directors	16
Litigation settlement amount				$ 37,000
Litigation settlement reserve for reimbursement of contingent fees and expenses				3,000
WMMRC [Member] | Runoff Notes [Member]
Related Party Transaction [Line Items]
Principal amount of Runoff Notes | $ / shares		$ 1.00
WMMRC [Member] | Investment Management Agreement And Administrative Services Agreement [Member]
Related Party Transaction [Line Items]
Expenses incurred under the agreements		$ 1,000	$ 1,100
WMMRC [Member] | Investment Management Agreement [Member]
Related Party Transaction [Line Items]
Description of fee		fee equal to the product of (x) the ending dollar amount of assets under management during the calendar month in question and (y) .002 divided by 12.
WMI Holdings Corp [Member]
Related Party Transaction [Line Items]
Litigation settlement reserve for reimbursement of contingent fees and expenses		$ 2,500
Other income				7,800
KKR Capital Markets LLC [Member] | Redeemable Convertible Series B Preferred Stock [Member]
Related Party Transaction [Line Items]
Payment of stock offering fee				8,250
Payment of additional deferred Fee				$ 8,250