Commitments and Contingencies - Estimated Amounts of Regular, Discharge Payments Expect to Pay and Estimated Recoveries from Charged-off Loans (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Summary Of Projections Of Estimated Payments And Recoveries [Line Items]
Estimated Regular Payments	$ 45,866
Estimated Discharge Payments	75,218
Estimated Total Payments	121,084
Estimated Recoveries	(4,100)
2015 [Member]
Summary Of Projections Of Estimated Payments And Recoveries [Line Items]
Estimated Regular Payments	13,400
Estimated Discharge Payments	2,709
Estimated Total Payments	16,109
Estimated Recoveries	(1,240)
2016 [Member]
Summary Of Projections Of Estimated Payments And Recoveries [Line Items]
Estimated Regular Payments	15,835
Estimated Discharge Payments	0
Estimated Total Payments	15,835
Estimated Recoveries	(1,240)
2017 [Member]
Summary Of Projections Of Estimated Payments And Recoveries [Line Items]
Estimated Regular Payments	16,631
Estimated Discharge Payments	0
Estimated Total Payments	16,631
Estimated Recoveries	(1,240)
2018 and Later [Member]
Summary Of Projections Of Estimated Payments And Recoveries [Line Items]
Estimated Regular Payments	0
Estimated Discharge Payments	72,509
Estimated Total Payments	72,509
Estimated Recoveries	$ (380)