Fair Value of Assets and Liabilities - Loans, Loan Servicing Rights, Related Notes and Certificates (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	$ 4,716,156	$ 4,556,081
Securities available for sale:	284,300	297,211
Servicing assets	16,964	10,250
Total assets	5,017,420	4,863,542
Notes and certificates	4,713,449	4,571,583
Servicing liabilities	2,827	3,973
Total liabilities	4,716,276	4,575,556
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	209,171	215,751
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	48,079	54,409
U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	16,583	16,578
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	3,516	3,485
Other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	6,951	6,988
Level 1 Inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Securities available for sale:	0	0
Servicing assets	0	0
Total assets	0	0
Notes and certificates	0	0
Servicing liabilities	0	0
Total liabilities	0	0
Level 1 Inputs | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	0	0
Level 1 Inputs | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	0	0
Level 1 Inputs | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	0	0
Level 1 Inputs | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	0	0
Level 1 Inputs | Other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	0	0
Level 2 Inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Securities available for sale:	284,300	297,211
Servicing assets	0	0
Total assets	284,300	297,211
Notes and certificates	0	0
Servicing liabilities	0	0
Total liabilities	0	0
Level 2 Inputs | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	209,171	215,751
Level 2 Inputs | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	48,079	54,409
Level 2 Inputs | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	16,583	16,578
Level 2 Inputs | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	3,516	3,485
Level 2 Inputs | Other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	6,951	6,988
Level 3 Inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	4,716,156	4,556,081
Securities available for sale:	0	0
Servicing assets	16,964	10,250
Total assets	4,733,120	4,566,331
Notes and certificates	4,713,449	4,571,583
Servicing liabilities	2,827	3,973
Total liabilities	4,716,276	4,575,556
Level 3 Inputs | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	0	0
Level 3 Inputs | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	0	0
Level 3 Inputs | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	0	0
Level 3 Inputs | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	0	0
Level 3 Inputs | Other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale:	$ 0	$ 0