Premises and Equipment, Net - Schedule of Premises and Equipment, Net (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Premises and equipment	$ 84,255	$ 301,944
Less: accumulated depreciation and amortization	(17,995)	(251,731)
Premises and equipment, net	66,260	50,213
Computer Software [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment	$ 74,050	$ 246,271
Computer Software [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful Life	3 years	3 years
Computer Software [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful Life	7 years	7 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment	$ 6,131	$ 12,699
Leasehold Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful Life	2 years	2 years
Leasehold Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful Life	9 years	9 years
Computer Hardware [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment	$ 2,154	$ 33,154
Useful Life	3 years	3 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment	$ 165	$ 7,812
Useful Life	3 years	3 years
Assets in Development [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment	$ 1,755	$ 2,008