Accumulated Other Comprehensive Income (Reclassification out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment securities gains, net			$ 1,300	$ 552
Compensation and employee benefits	$ 35,175	$ 32,559	112,721	94,961
Total before tax	37,295	31,188	104,282	89,698
Income tax provision	(11,515)	(9,605)	(32,195)	(27,044)
Net income	25,780	21,583	72,087	62,654
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment securities gains, net	236	33	1,300	552
Total before tax	236	33	1,300	552
Income tax provision	(85)	(12)	(471)	(200)
Net income	151	21	829	352
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains and Losses on Pension Plan Liability [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Compensation and employee benefits	(97)	(36)	(240)	(111)
Total before tax	(97)	(36)	(240)	(111)
Income tax provision	35	13	87	40
Net income	$ (62)	$ (23)	$ (153)	$ (71)