Changes In Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 159,185	$ 159,185
Accumulated Amortization	118,774	112,403
Net Carrying Amount	40,411	46,782
Core deposit intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	47,527	36,497
Accumulated Amortization	37,371	33,613
Net Carrying Amount	10,156	2,884
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	107,460	104,560
Accumulated Amortization	77,933	73,496
Net Carrying Amount	29,527	31,064
Other intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,198	3,247
Accumulated Amortization	3,470	2,841
Net Carrying Amount	$ 728	406
Core deposit intangible-Marquette Acquisition [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount		11,030
Accumulated Amortization		1,838
Net Carrying Amount		9,192
Customer relationships - Marquette Acquisition [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount		2,900
Accumulated Amortization		338
Net Carrying Amount		2,562
Other intangible assets - Marquette Acquisition [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount		951
Accumulated Amortization		277
Net Carrying Amount		$ 674