Derivative Financial Instruments (Rollforward Of Amounts In Accumulated Other Comprehensive Income Related To Interest Rate Swaps Designated As Cash Flow Hedges) (Detail) - Interest Rate Contract - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Rollforward of AOCI from Cash Flow Hedging Derivatives [Roll Forward]
Unrealized gain at beginning of period	$ 11,902	$ 6,944
Amount reclassified from accumulated other comprehensive loss to interest expense on deposits and junior subordinated debentures	(680)	356
Amount of gain recognized in other comprehensive income	3,755	1,259
Unrealized gain at end of period	$ 14,977	$ 8,559