Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income Reclassifications) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized securities gains	$ 19,707	$ 60	$ 21,278	$ 8,202
Compensation and benefits, which includes pension expense.			(5,352)	(1,142)
Net unrealized gains on available for sale securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification for the period, tax			14	5
Net unrealized foreign exchange losses [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification for the period, tax			1,086	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.			(1,297)	(1,150)
Reclassification for the period, tax			(604)	(526)
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			24	8
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 and other expenses			$ (5,310)	$ 0