Accumulated Other Comprehensive Income (Reclassification out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment securities gains, net			$ 1,174	$ 1,300
Compensation and employee benefits	$ 38,476	$ 35,175	112,086	112,721
Total before tax	39,608	37,295	106,746	104,282
Income tax provision	(12,124)	(11,515)	(32,598)	(32,195)
Net income	27,484	25,780	74,148	72,087
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	572	236	1,174	1,300
Total before tax	572	236	1,174	1,300
Income tax provision	(208)	(85)	(426)	(471)
Net income	364	151	748	829
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	(167)	(97)	(501)	(240)
Total before tax	(167)	(97)	(501)	(240)
Income tax provision	60	35	182	87
Net income	$ (107)	$ (62)	$ (319)	$ (153)