Loans Held for Investment, net - Residential and Consumer Gross Loans Based on Accrual Status (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Accrual	$ 1,623,610	$ 1,543,790
Total	1,640,853	1,573,020	$ 1,621,554
Education
Financing Receivable, Impaired [Line Items]
Accrual	80,499	95,921
Residential and Consumer Loans Based on Accrual Status
Financing Receivable, Impaired [Line Items]
Accrual	842,747	866,268
Non-Accrual	5,982	6,729
Total	848,729	872,997
Residential
Financing Receivable, Impaired [Line Items]
Accrual	528,171	526,148
Total	529,775	531,131	529,777
Residential | Residential and Consumer Loans Based on Accrual Status
Financing Receivable, Impaired [Line Items]
Accrual	524,780	525,258
Non-Accrual	4,995	5,873
Total	529,775	531,131
Consumer loans
Financing Receivable, Impaired [Line Items]
Total	318,954	341,866	$ 367,831
Consumer loans | Education
Financing Receivable, Impaired [Line Items]
Total	91,671	108,384
Consumer loans | Other consumer
Financing Receivable, Impaired [Line Items]
Accrual	226,129	232,207
Total	227,283	233,482
Consumer loans | Residential and Consumer Loans Based on Accrual Status | Education
Financing Receivable, Impaired [Line Items]
Accrual	91,480	108,179
Non-Accrual	191	205
Total	91,671	108,384
Consumer loans | Residential and Consumer Loans Based on Accrual Status | Other consumer
Financing Receivable, Impaired [Line Items]
Accrual	226,487	232,831
Non-Accrual	796	651
Total	$ 227,283	$ 233,482