Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity) - Components of Mortgage Banking Activity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Mortgage Loan Activity [Line Items]
Balance, beginning of period	$ 267,475
Originations	536,673
Sales	(634,540)
Balance, end of period	188,037
Gains on sales	18,429
Total mortgage income	18,931	13,718
Mortgage loans held for sale [Member]
Mortgage Loan Activity [Line Items]
Balance, beginning of period	267,475	153,013
Balance acquired during the period
Originations	536,673	450,644
Sales	(616,111)	(475,532)
Balance, end of period	188,037	128,125
Mortgage income [Member]
Mortgage Loan Activity [Line Items]
Fair value changes of derivatives and mortgage loans held for sale, net	364	56
Gains on sales	18,429	13,563
Servicing and other income, net	138	99
Total mortgage income	$ 18,931	$ 13,718