Finance Receivables and Allowance for Credit Losses - Schedule of Past Due Financing Receivables (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing	$ 328	$ 916
Nonaccrual	131,407	132,373
Financing Receivables, Past Due	170,573	153,645
Current	8,839,939	6,794,760
30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	31,260	16,266
60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	7,578	4,090
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing	23	565
Nonaccrual	56,585	57,536
Financing Receivables, Past Due	57,734	59,003
Current	1,859,365	1,745,612
Commercial [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	847	802
Commercial [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	279	100
Construction [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	2,769	749
Financing Receivables, Past Due	2,769	749
Current	196,740	184,700
Other [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	41,257	46,601
Financing Receivables, Past Due	43,059	47,174
Current	2,888,285	1,615,198
Other [Member] | Commercial Real Estate [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	1,652	438
Other [Member] | Commercial Real Estate [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	150	135
Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing	2	114
Nonaccrual	17,674	14,953
Financing Receivables, Past Due	39,232	26,613
Current	2,048,298	1,618,001
Residential [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	17,786	9,300
Residential [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	3,770	2,246
Consumer Home Equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	4,431	2,369
Financing Receivables, Past Due	6,365	3,054
Current	470,074	356,900
Consumer Home Equity [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	1,511	283
Consumer Home Equity [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	423	402
Consumer Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing	242	202
Nonaccrual	1,623	1,573
Financing Receivables, Past Due	8,805	6,309
Current	1,158,932	1,044,027
Consumer Auto [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	5,903	3,804
Consumer Auto [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	1,037	730
Consumer - Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing	61	25
Nonaccrual	7,068	1,256
Financing Receivables, Past Due	12,609	2,276
Current	218,245	131,202
Consumer - Other [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	3,561	830
Consumer - Other [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	$ 1,919	165
Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing		10
Nonaccrual		7,336
Financing Receivables, Past Due		8,467
Current		99,120
Covered Loans [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due		809
Covered Loans [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due		$ 312