Credit Risk Profile Based on Payment Activity - Loans Accounted for under ASC 310-30 (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	$ 10,083,266	$ 9,430,761	$ 8,916,128
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	395,216		$ 380,938
Other [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	124,863	154,777
Other [Member] | Consumer [Member] | Loans Accounted for under ASC 310-30 [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	1,230	2,001
Other [Member] | Performing [Member] | Consumer [Member] | Loans Accounted for under ASC 310-30 [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	$ 1,230	$ 2,001