Reclassification out of accumulated other comprehensive income (loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Personnel costs	$ 114,679	$ 116,336	$ 230,668	$ 237,827
Net Gain Loss And Valuation Adjustments On Investment Securities	5,856	(349)	5,856	(349)
Trading Gains (Losses)	7,900	(7,283)	7,825	(9,426)
Income Tax Expense Benefit	(237,380)	(77,893)	(294,257)	(61,701)
Net Income	327,468	65,739	207,161	114,147
Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net Income	(1,076)	(7,426)	(5,288)	(13,561)
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	(6,169)	(6,240)	(12,338)	(12,479)
Income Tax Expense Benefit	2,962	1,725	4,813	3,450
Net Income	(3,207)	(4,515)	(7,525)	(9,029)
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	(6,169)	(6,290)	(12,338)	(12,579)
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	0	50	0	100
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain Loss [Member] | Realized Gain Loss On Sale Of Investments [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest	0	(349)	0	(349)
Net Gain Loss And Valuation Adjustments On Investment Securities	0	(349)	0	(349)
Income Tax Expense Benefit	0	0	0	0
Net Income	0	(349)	0	(349)
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	3,045	(3,660)	3,196	(5,976)
Trading Gains (Losses)	3,045	(3,660)	3,196	(5,976)
Income Tax Expense Benefit	(914)	1,098	(959)	1,793
Net Income	$ 2,131	$ (2,562)	$ 2,237	$ (4,183)