Goodwill and Other Intangible Assets (Gross Carrying Value And Accumulated Amortization Of Other Intangible Assets) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 92,420	$ 92,420
Accumulated Amortization	(58,746)	(53,094)
Net Carrying Amount	33,674	39,326
Goodwill	538,373	538,373
Community Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	516,560	516,560
HSA Bank [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	43,000	43,000
Accumulated Amortization	(9,326)	(4,817)
Net Carrying Amount	33,674	38,183
Goodwill	21,813	21,813
Core Deposits [Member] | Community Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	49,420	49,420
Accumulated Amortization	(49,420)	(48,277)
Net Carrying Amount	0	1,143
Core Deposits [Member] | HSA Bank [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	22,000	22,000
Accumulated Amortization	(6,162)	(3,269)
Net Carrying Amount	15,838	18,731
Customer Relationships [Member] | HSA Bank [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	21,000	21,000
Accumulated Amortization	(3,164)	(1,548)
Net Carrying Amount	$ 17,836	$ 19,452