Loans (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Schedule Of Accretable Yield Activity Related to Loans Acquired With Evidence Of Credit Quality Deterioration Since Origination Table [Line Items]
Net deferred loan fees and costs and fair value accounting adjustments	$ 6,500	$ 8,000	$ 6,500	$ 8,000	$ 9,300
Accretable yield amortized to interest income	4,144	5,025	12,915	16,101
Premium finance receivables
Schedule Of Accretable Yield Activity Related to Loans Acquired With Evidence Of Credit Quality Deterioration Since Origination Table [Line Items]
Unearned income portion of premium finance receivables	$ 98,100	$ 80,400	$ 98,100	$ 80,400	$ 87,000