Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income Reclassifications) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized securities gains	$ 460	$ 728
Other income	326,912	58,923
Income tax provision (benefit)	104,174	(83,361)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Compensation and benefits, which includes pension expense.	(4,510)	(374)
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	(18)	26
Reclassification for the period, tax	(11)	14
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
Reclassification for the period, tax	1,097	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | 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.	(433)	(400)
Reclassification for the period, tax	(204)	(178)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Other pension [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax provision (benefit)	1,231	0
Reclassification for the period, tax	$ (1,231)	$ 0