Goodwill and Other Intangible Assets (Gross Carrying Value And Accumulated Amortization Of Other Intangible Assets) (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 538,373,000	$ 538,373,000
Gross Carrying Amount	43,000,000	43,000,000
Accumulated Amortization	(21,083,000)	(17,236,000)
Net Carrying Amount	21,917,000	25,764,000
Community Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	516,600,000
HSA Bank [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	21,800,000
Core Deposits [Member] | HSA Bank [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	22,000,000	22,000,000
Accumulated Amortization	(13,073,000)	(10,842,000)
Net Carrying Amount	8,927,000	11,158,000
Customer Relationships [Member] | HSA Bank [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	21,000,000	21,000,000
Accumulated Amortization	(8,010,000)	(6,394,000)
Net Carrying Amount	$ 12,990,000	$ 14,606,000