Components of deferred tax assets and liabilities (Detail) - Entity [Domain] - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Deferred Tax Assets Gross Abstract
Deferred Tax Assets Tax Credit Carryforwards Other	$ 12,508	$ 12,056
Deferred Tax Asset Operating Loss Carryforwards And Other Carryforwards	1,263,589	1,261,413
Deferred Tax Assets Tax Deferred Expense Compensation And Benefits	109,451	111,677
Allowance for loan losses	694,981	710,666
Deferred Tax Assets Depreciation	7,530	7,915
Other temporary differences	27,165	27,755
Total gross deferred tax assets	2,132,394	2,149,690
Deferred Tax Liabilities Abstract
Deferred Tax Liabilities Deferred Expense Deferred Policy Acquisition Cost	42,241	37,804
Deferred Tax Liabilities Parents Basis In Discontinued Operation	0	0
FDIC-assisted transaction	84,876	81,335
Deferred Tax Liabilities, Investments	24,754	20,817
Other temporary differences	22,696	18,093
Total gross deferred tax liabilities	174,567	158,049
Valuation allowance	672,391	1,212,748
Net deferred tax asset	1,285,436	778,893
Loans Member
Deferred Tax Assets Gross Abstract
Deferred Tax Assets Deferred Income	7,543	7,720
Deferred Tax Liabilities Abstract
Deferred Tax Liabilities Deferred Expense Deferred Financing Costs	0	0
Sale Leaseback [Member]
Deferred Tax Assets Gross Abstract
Deferred Tax Assets Deferred Income	6,735	7,500
Intercompany [Member]
Deferred Tax Assets Gross Abstract
Deferred Tax Assets Deferred Income	$ 2,892	$ 2,988