Reclassification out of accumulated other comprehensive income (loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended					9 Months Ended
	Sep. 30, 2014		Mar. 31, 2014	Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment for (gains) losses included in net income (loss)	$ 0	[1]	$ (7,700)	$ 0	[1]	$ (7,718)	[1]	$ 0	[1]
Net Income	62,573			229,135		(362,332)		436,296
Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net Income	362			(2,874)		(11,002)		(8,449)
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	(1,177)			(6,168)		(3,529)		(18,506)
Income Tax Expense Benefit	459			2,406		1,376		7,219
Net Income	(718)			(3,762)		(2,153)		(11,287)
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	(2,127)			(6,168)		(6,379)		(18,506)
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			0		2,850		0
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	(1,120)			1,456		(4,745)		4,652
Mortgage banking activities	(1,120)			1,456		(4,745)		4,652
Income Tax Expense Benefit	437			(568)		1,851		(1,814)
Net Income	(683)			888		(2,894)		2,838
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		(7,718)		0
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		(7,718)		0
Noninterest Income Other Operating Income	$ 0			$ 0		$ (7,718)		$ 0

[1] All amounts presented are net of tax.