Credit Risk Profile Based on Payment Activity - Originated and Non-PCI Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	$ 11,964,724	$ 11,280,513	$ 10,997,028
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	375,250		422,450
Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	5,611	23,967	$ 24,445
Commercial - credit card [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	200,286	172,291
Real estate - HELOC [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	563,551	648,379
Credit card [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	216,457	252,697
Other [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	158,793	151,783
Originated and Non-PCI Loans [Member] | Real estate - residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	688,413	638,591
Originated and Non-PCI Loans [Member] | Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	5,611	23,967
Originated and Non-PCI Loans [Member] | Commercial - credit card [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	200,286	172,291
Originated and Non-PCI Loans [Member] | Real estate - HELOC [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	563,551	648,379
Originated and Non-PCI Loans [Member] | Credit card [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	216,457	252,697
Originated and Non-PCI Loans [Member] | Other [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	158,793	151,783
Originated and Non-PCI Loans [Member] | Performing [Member] | Real estate - residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	687,611	637,662
Originated and Non-PCI Loans [Member] | Performing [Member] | Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	5,611	23,967
Originated and Non-PCI Loans [Member] | Performing [Member] | Commercial - credit card [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	200,286	172,291
Originated and Non-PCI Loans [Member] | Performing [Member] | Real estate - HELOC [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	560,116	645,366
Originated and Non-PCI Loans [Member] | Performing [Member] | Credit card [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	215,995	252,385
Originated and Non-PCI Loans [Member] | Performing [Member] | Other [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	158,740	151,747
Originated and Non-PCI Loans [Member] | Non-performing [Member] | Real estate - residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	802	929
Originated and Non-PCI Loans [Member] | Non-performing [Member] | Real estate - HELOC [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	3,435	3,013
Originated and Non-PCI Loans [Member] | Non-performing [Member] | Credit card [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	462	312
Originated and Non-PCI Loans [Member] | Non-performing [Member] | Other [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	$ 53	$ 36