Reclassification out of accumulated other comprehensive income (loss) (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment for (gains) losses included in net income (loss)	[1]	$ 0	$ 0	$ 0	$ (7,718)
Other Comprehensive Income Loss Reclassification Adjustment From AOCI For Writedown Of Securities Before Tax		14,445	0	14,445	0
Net Income		597,452	(511,314)	672,278	(424,905)
Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net Income		(15,021)	(1,815)	(18,334)	(11,364)
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Realized Gain Loss On Sale Of Investments Securities [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest		(14,440)	0	(14,440)	0
Net Gain Loss And Valuation Adjustments On Investment Securities		5	0	5	0
Income Tax Expense Benefit		2,485	0	2,485	0
Net Income		(11,955)	0	(11,955)	0
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest		(4,075)	(1,176)	(8,150)	(2,352)
Income Tax Expense Benefit		1,589	459	3,178	917
Net Income		(2,486)	(717)	(4,972)	(1,435)
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member] | Defined Benefit Plan Amortization Of Gains Losses [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Personnel costs		(5,025)	(2,126)	(10,050)	(4,252)
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member] | Defined Benefit Plan Amortization Of Prior Service Cost Credit [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Personnel costs		950	950	1,900	1,900
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member] | Forward Contracts [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest		(951)	(1,800)	(2,309)	(3,624)
Mortgage banking activities		(951)	(1,800)	(2,309)	(3,624)
Income Tax Expense Benefit		371	702	902	1,413
Net Income		(580)	(1,098)	(1,407)	(2,211)
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Accumulated Translation Adjustment
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net Income		0	0	0	(7,718)
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Accumulated Translation Adjustment | Cumulative Translation Adjustment Reclassified Into Earnings [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest		0	0	0	(7,718)
Noninterest Income Other Operating Income		$ 0	$ 0	$ 0	$ (7,718)

[1] All amounts presented are net of tax.