Capital Stock - Additional Information (Detail) - USD ($)				1 Months Ended	3 Months Ended				9 Months Ended			12 Months Ended
	May. 15, 2015	Apr. 28, 2015	Jan. 05, 2015	Jan. 30, 2015	Sep. 30, 2015	Mar. 31, 2015	Mar. 31, 2014	Mar. 19, 2012	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	May. 11, 2015	May. 10, 2015	Jan. 30, 2014	Dec. 31, 2013
Capital Stock Distribution [Line Items]
Common stock, shares authorized					3,500,000,000				3,500,000,000	3,500,000,000		3,500,000,000	3,500,000,000	500,000,000
Preferred stock, shares authorized					10,000,000				10,000,000	10,000,000			10,000,000	5,000,000
Common stock, par value					$ 0.00001				$ 0.00001	$ 0.00001		$ 0.00001	$ 0.00001	$ 0.00001
Preferred stock, par value					$ 0.00001				$ 0.00001	$ 0.00001			$ 0.00001	$ 0.00001
Conversion of shares													1
Warrants to purchase in aggregate, shares															61,400,000
Preferred deemed dividend							$ 9,455,000				$ 9,455,000
Warrants expiration period										5 years
Maximum percent of the voting shares of the emerging entity immediately prior to the confirmation of reorganization				42.50%	50.00%				50.00%	50.00%
Registration right period										180 days
Escrow deposit			$ 598,500,000
Derivative liability - embedded conversion feature					$ 132,144,000				$ 132,144,000	$ 132,144,000
Changes in fair value					9,281,000					$ (65,917,000)
Award vesting period										3 years
Unamortized value of unvested restricted share grant					$ 10,215,000				$ 10,215,000	$ 10,215,000		$ 1,200,000
Equity-based compensation										$ 961,000	$ 600,000
Per share of unvested shares of common stock										$ 0.0001
Vested number of shares						190,070
Vested number of shares, outstanding						113,146
Vested number of shares, issued		76,924
Expected increase in additional paid in capital due to early vesting of equity shares										$ 382,000
Expected increase in share based compensation due to early vesting of equity shares										$ 382,000
Common stock, shares outstanding					206,168,035				206,168,035	206,168,035		202,343,245
Warrants to purchase common stock, outstanding					61,400,000				61,400,000	61,400,000		61,400,000
EXEC Grants [Member]
Capital Stock Distribution [Line Items]
Share price	$ 2.76
Restricted stock fair value										$ 9,200,000
Restricted stock price per share										$ 2.60
Restricted stock award [Member]
Capital Stock Distribution [Line Items]
Amount of restricted stock grants												$ 600,000
Share price	$ 2.76	$ 2.60
Unvested shares					6,168,035				6,168,035	6,168,035		2,343,245				1,842,351
Number of Restricted Stock Awards Outstanding, Restricted stock awards granted	3,555,556	269,234								3,824,790		500,894
Restricted stock award [Member] | EXEC Grants [Member]
Capital Stock Distribution [Line Items]
Amount of restricted stock grants	$ 9,800,000
Restricted shares subject to repurchase [Member]
Capital Stock Distribution [Line Items]
Unvested shares					4,197,396				4,197,396	4,197,396		1,343,764				1,456,987
Number of Restricted Stock Awards Outstanding, Restricted stock awards granted										3,824,790		500,894
Members of Board [Member] | Restricted stock award [Member]
Capital Stock Distribution [Line Items]
Amount of restricted stock grants		$ 700,000										$ 700,000
Chief Executive Officer [Member] | Restricted stock award [Member]
Capital Stock Distribution [Line Items]
Number of Restricted Stock Awards Outstanding, Restricted stock awards granted	1,777,778
Chief Operating Officer [Member] | Restricted stock award [Member]
Capital Stock Distribution [Line Items]
Number of Restricted Stock Awards Outstanding, Restricted stock awards granted	1,777,778
Minimum [Member]
Capital Stock Distribution [Line Items]
Preferred stock liquidation preference per share					$ 10.00				$ 10.00	$ 10.00
Convertible Series A Preferred Stock [Member]
Capital Stock Distribution [Line Items]
Preferred stock, par value					$ 0.00001				$ 0.00001	$ 0.00001		$ 0.00001
Preferred stock, shares issued					1,000,000				1,000,000	1,000,000		1,000,000			1,000,000
Purchase price of convertible preferred stock maximum limit															$ 11,100,000
Preferred stock liquidation preference										The Series A Preferred Stock has rights substantially similar to those associated with WMIH’s common stock, with the exception of a liquidation preference, conversion rights and customary anti-dilution protections. The Series A Preferred Stock has a liquidation preference equal to the greater of (i) $10.00 per one million shares of Series A Preferred Stock plus declared but unpaid dividends on such shares and (ii) the amount that the holder would be entitled to in a relevant transaction had the Series A Preferred Stock been converted to common stock of WMIH.
Convertible preferred stock conversion price										$ 1.10
Preferred stock, shares outstanding					1,000,000				1,000,000	1,000,000		1,000,000
Convertible Preferred Stock [Member]
Capital Stock Distribution [Line Items]
Expiration of right to participating into future offering				Jan. 30, 2017
Preferred stock participation right										Additionally, until January 30, 2017, the Series A Holders will have the right to purchase up to 50% of any future equity rights offerings or other equity issuance by WMIH on the same terms as the equity issued to other investors in such transactions, in an aggregate amount of such offerings and issuances by WMIH of up to $1.0 billion
Convertible Preferred Stock [Member] | Maximum [Member]
Capital Stock Distribution [Line Items]
Maximum percent of the voting common shares of the emerging entity immediately prior to the confirmation of reorganization				50.00%
Percentage of rights vest with preferred shareholders to future offering				50.00%
Preferred stock participation value				$ 1,000,000,000
Redeemable Convertible Preferred Stock [Member]
Capital Stock Distribution [Line Items]
Preferred stock, par value			$ 0.00001
Preferred stock liquidation preference per share			$ 1,000
Preferred stock, shares issued			600,000		600,000				600,000	600,000		0
Preferred stock dividend rate calculated on interest rate			3.00%
Number of trading periods										20 days
Conversion floor price of common stock					$ 1.75				$ 1.75	$ 1.75
Derivative liability - embedded conversion feature			$ 66,200,000		$ 132,100,000				$ 132,100,000	$ 132,100,000
Changes in fair value									$ 65,900,000
Share price	$ 2.25
Preferred stock, shares outstanding					600,000				600,000	600,000		0
Redeemable Convertible Preferred Stock [Member] | Minimum [Member]
Capital Stock Distribution [Line Items]
Preferred stock liquidation preference per share			$ 1,000
Redeemable Convertible Preferred Stock [Member] | Maximum [Member]
Capital Stock Distribution [Line Items]
Conversion ceiling price of common stock					$ 2.25				$ 2.25	$ 2.25
Common Stock [Member]
Capital Stock Distribution [Line Items]
Issuance of common stock, Shares								200,000,000
Warrant One [Member]
Capital Stock Distribution [Line Items]
Warrants to purchase common stock															30,700,000
Warrants to purchase common stock, exercise price															$ 1.32
Warrant Two [Member]
Capital Stock Distribution [Line Items]
Warrants to purchase common stock															30,700,000
Warrants to purchase common stock, exercise price															$ 1.43