Accumulated Other Comprehensive Income (Reclassification out of AOCI) (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]
Investment securities gains, net			$ 0	$ 602
Compensation and employee benefits	$ 38,393	$ 37,291	79,218	73,610
Total before tax	38,252	36,650	78,025	67,138
Income tax provision	(11,120)	(11,245)	(21,694)	(20,474)
Net income	27,132	25,405	56,331	46,664
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	0	229	0	602
Total before tax	0	229	0	602
Income tax provision	0	(83)	0	(218)
Net income	0	146	0	384
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	(71)	(167)	(207)	(334)
Total before tax	(71)	(167)	(207)	(334)
Income tax provision	26	61	75	122
Net income	$ (45)	$ (106)	$ (132)	$ (212)