Goodwill And Other Intangible Assets (Summary of Intangible Assets) (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Total other intangible assets, net	$ 27,378	$ 17,621	$ 18,651
Community banking
Finite-Lived Intangible Assets [Line Items]
Total net carrying amount	22,053	11,845	12,722
Trademark | Community banking
Finite-Lived Intangible Assets [Line Items]
Carrying amount	5,800	0	0
Core deposit intangibles | Community banking
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	44,395	37,272	37,272
Accumulated amortization	(28,142)	(25,427)	(24,550)
Net carrying amount	16,253	11,845	12,722
Customer list intangibles | Specialty finance
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	1,967	1,972	1,972
Accumulated amortization	(1,407)	(1,298)	(1,258)
Net carrying amount	560	674	714
Customer list and other intangibles | Wealth management
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	7,940	7,940	7,940
Accumulated amortization	(3,175)	(2,838)	(2,725)
Net carrying amount	$ 4,765	$ 5,102	$ 5,215