Changes in level 3 assets and liabilities measured at fair value on a recurring basis (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	$ 174,485	$ 176,097	$ 180,773	$ 178,057
Gains (Losses) included in earnings	(8,249)	(5,315)	(16,610)	(11,115)
Gains (losses) included in OCI	(39)	(85)	(81)	(86)
Additions	3,664	5,301	7,606	10,480
Sales	0	(324)	(1,109)	(699)
Settlements	(1,162)	(1,444)	(1,880)	(2,407)
Ending Balance	168,699	174,230	168,699	174,230
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	(3,254)	2,604	(6,445)	3,964
Liabilities, Fair Value Disclosure [Abstract]
Beginning Balance	(126,345)	(118,777)	(128,299)	(112,002)
Gains (Losses) included in earnings	(1,206)	(476)	(38)	(7,251)
Gains (losses) included in OCI	0	0	0	0
Additions	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	786	0
Ending Balance	(127,551)	(119,253)	(127,551)	(119,253)
Fair Value Liabilities Measured On Recurring Basis Change In Unrealized Gain Loss	(1,206)	(476)	(38)	(7,251)
Other Liabilities Member | Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Contingent Liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Beginning Balance	(126,345)	(118,777)	(128,299)	(112,002)
Gains (Losses) included in earnings	(1,206)	(476)	(38)	(7,251)
Gains (losses) included in OCI	0	0	0	0
Additions	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	786	0
Ending Balance	(127,551)	(119,253)	(127,551)	(119,253)
Fair Value Liabilities Measured On Recurring Basis Change In Unrealized Gain Loss	(1,206)	(476)	(38)	(7,251)
Available For Sale Securities Member | Collateralized Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	6,379	7,043	6,523	7,070
Gains (Losses) included in earnings	(1)	(2)	(3)	(3)
Gains (losses) included in OCI	(39)	(85)	(81)	(86)
Additions	0	0	0	0
Sales	0	0	0	0
Settlements	(170)	(200)	(270)	(225)
Ending Balance	6,169	6,756	6,169	6,756
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	0	0	0	0
Trading Account Assets[Member] | Collateralized Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	8,301	10,937	9,799	11,818
Gains (Losses) included in earnings	(75)	(83)	(114)	(174)
Gains (losses) included in OCI	0	0	0	0
Additions	500	231	651	258
Sales	0	0	(1,109)	0
Settlements	(924)	(750)	(1,425)	(1,567)
Ending Balance	7,802	10,335	7,802	10,335
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	(41)	(14)	(65)	(45)
Trading Account Assets[Member] | Collateralized Mortgage Obligations Member
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	1,561	2,025	1,423	2,499
Gains (Losses) included in earnings	(1)	(3)	(11)	1
Gains (losses) included in OCI	0	0	0	0
Additions	0	20	263	25
Sales	0	(324)	0	(699)
Settlements	(66)	(65)	(181)	(173)
Ending Balance	1,494	1,653	1,494	1,653
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	(1)	1	(8)	3
Trading Account Assets[Member] | Other Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	1,715	2,143	1,929	2,240
Gains (Losses) included in earnings	(432)	(101)	(646)	(198)
Gains (losses) included in OCI	0	0	0	0
Additions	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Ending Balance	1,283	2,042	1,283	2,042
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	(394)	48	(530)	(7)
Mortgage Servicing Rights Member
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	156,529	153,949	161,099	154,430
Gains (Losses) included in earnings	(7,740)	(5,126)	(15,836)	(10,741)
Gains (losses) included in OCI	0	0	0	0
Additions	3,164	5,050	6,692	10,197
Sales	0	0	0	0
Settlements	(2)	(429)	(4)	(442)
Ending Balance	151,951	153,444	151,951	153,444
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	$ (2,818)	$ 2,569	$ (5,842)	$ 4,013