Changes in Finite-Lived Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 144,184	$ 143,704
Accumulated Amortization	94,296	88,119
Net Carrying Amount	49,888	55,585
Core deposit intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	36,497	36,497
Accumulated Amortization	32,217	31,674
Net Carrying Amount	4,280	4,823
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	104,440	103,960
Accumulated Amortization	59,582	54,062
Net Carrying Amount	44,858	49,898
Other intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,247	3,247
Accumulated Amortization	2,497	2,383
Net Carrying Amount	$ 750	$ 864