Mortgage banking activities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Mortgage Servicing Fees Excluding Fair Value	$ 11,500	$ 12,200	$ 34,100	$ 36,300
Mortgage Servicing Rights MSR Impairment Recovery			6,862	7,217
Net gain on sale of loans, including valuation adjustments on loans held-for-sale	3,454	(1,205)	(54,532)	(30,459)
Trading Gains (Losses)	(6,607)	5,443	(11,936)	6,040
Mortgage banking activities	18,896	21,847	57,281	60,418
Mortgage Banking Activities [Member]
Mortgage Servicing Fees Excluding Fair Value	11,547	12,282	34,110	36,339
Mortgage Servicing Rights MSR Impairment Recovery	3,879	(2,426)	(6,862)	(7,217)
Servicing Fees Net	15,426	9,856	27,248	29,122
Net gain on sale of loans, including valuation adjustments on loans held-for-sale	3,559	19,700	16,968	49,028
Unrealized Gain (Loss) on Derivatives	(865)	(58)	(265)	(154)
Gain (Loss) on Sale of Derivatives	776	(7,651)	13,330	(17,578)
Trading Gains (Losses)	(89)	(7,709)	13,065	(17,732)
Mortgage banking activities	$ 18,896	$ 21,847	$ 57,281	$ 60,418