Commitments and Contingencies - Estimated Amounts of Regular, Discharge Payments Expected to Pay and Estimated Recoveries from Charged-off Loans (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2015 USD ($)
Summary Of Projections Of Estimated Payments And Recoveries [Line Items]
Estimated Regular Payments	$ 41,632
Estimated Discharge Payments	70,908
Estimated Recoveries	(5,459)
Estimated Total Payments, Net	107,081
July 1 through December 31, 2015 [Member]
Summary Of Projections Of Estimated Payments And Recoveries [Line Items]
Estimated Regular Payments	0
Estimated Discharge Payments	0
Estimated Recoveries	0
Estimated Total Payments, Net	0
2016 [Member]
Summary Of Projections Of Estimated Payments And Recoveries [Line Items]
Estimated Regular Payments	24,017
Estimated Discharge Payments	0
Estimated Recoveries	(2,354)
Estimated Total Payments, Net	21,663
2017 [Member]
Summary Of Projections Of Estimated Payments And Recoveries [Line Items]
Estimated Regular Payments	17,615
Estimated Discharge Payments	0
Estimated Recoveries	(1,534)
Estimated Total Payments, Net	16,081
2018 and Later [Member]
Summary Of Projections Of Estimated Payments And Recoveries [Line Items]
Estimated Regular Payments	0
Estimated Discharge Payments	70,908
Estimated Recoveries	(1,571)
Estimated Total Payments, Net	$ 69,337