Note Fair value measurement (Changes in level 3 assets and liabilities measured at fair value on a recurring basis) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	$ 204,959	$ 221,811
Gains (Losses) included in earnings	(6,020)	(8,420)
Gains (losses) included in OCI	10	15
Additions	2,927	2,635
Sales	(361)	(1,226)
Settlements	(451)	(499)
Transfers into Level 3	0	0
Transfers out of Level 3	(88)	0
Ending Balance	200,976	214,316
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	(745)	(3,772)
Liabilities, Fair Value Disclosure [Abstract]
Beginning Balance	(153,158)	(120,380)
Gains (Losses) included in earnings	(7,385)	(443)
Gains (losses) included in OCI	0	0
Additions	0	0
Sales	0	0
Settlements	0	0
Transfer into Level 3	0	0
Transfer out of Level 3	0	0
Ending Balance	(160,543)	(120,823)
Fair Value Liabilities Measured On Recurring Basis Change In Unrealized Gain Loss	(7,385)	(443)
Other liabilities | Contingent consideration
Liabilities, Fair Value Disclosure [Abstract]
Beginning Balance	(153,158)	(120,380)
Gains (Losses) included in earnings	(7,385)	(443)
Gains (losses) included in OCI	0	0
Additions	0	0
Sales	0	0
Settlements	0	0
Transfer out of Level 3	0
Ending Balance	(160,543)	(120,823)
Fair Value Liabilities Measured On Recurring Basis Change In Unrealized Gain Loss	(7,385)	(443)
Available For Sale Securities | Mortgage Backed Securities
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	1,392	1,434
Gains (Losses) included in earnings	0	(2)
Gains (losses) included in OCI	10	15
Additions	0	0
Sales	0	0
Settlements	(25)	(25)
Transfers out of Level 3	(88)
Ending Balance	1,289	1,422
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	0	0
Trading account securities | Mortgage Backed Securities
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	4,755	6,454
Gains (Losses) included in earnings	(43)	89
Gains (losses) included in OCI	0	0
Additions	164	338
Sales	(156)	(1,120)
Settlements	(375)	(364)
Transfers out of Level 3	0
Ending Balance	4,345	5,397
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	(27)	86
Trading account securities | Collateralized Mortgage Obligations
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	1,321	1,831
Gains (Losses) included in earnings	(4)	(6)
Gains (losses) included in OCI	0	0
Additions	0	174
Sales	(205)	(106)
Settlements	(51)	(110)
Transfers out of Level 3	0
Ending Balance	1,061	1,783
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	(4)	(3)
Trading account securities | Other
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	602	687
Gains (Losses) included in earnings	(19)	(24)
Gains (losses) included in OCI	0	0
Additions	0	0
Sales	0	0
Settlements	0	0
Transfers out of Level 3	0
Ending Balance	583	663
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	9	11
Mortgage Servicing Rights
Assets, Fair Value Disclosure [Abstract]
Beginning Balance	196,889	211,405
Gains (Losses) included in earnings	(5,954)	(8,477)
Gains (losses) included in OCI	0	0
Additions	2,763	2,123
Sales	0	0
Settlements	0	0
Transfers out of Level 3	0
Ending Balance	193,698	205,051
Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss	$ (723)	$ (3,866)