Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income Reclassifications) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized securities gains	$ 1,111	$ 7,414	$ 1,571	$ 8,142
Other income	$ 133,970	$ 143,379	460,882	202,302
Compensation and benefits, which includes pension expense.			(4,451)	(758)
Net unrealized gains on available for sale securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification for the period, tax			271	6
Net unrealized foreign exchange losses [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification for the period, tax			1,097	0
Amortization of defined benefit pension plan actuarial gains (losses) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Compensation and benefits, which includes pension expense.			(859)	(767)
Reclassification for the period, tax			(403)	(351)
Other pension [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification for the period, tax			(1,231)	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Net unrealized gains on available for sale securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized securities gains			467	9
Reclassification out of Accumulated Other Comprehensive Income [Member] | Net unrealized foreign exchange losses [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income			$ (5,290)	$ 0