Accumulated Other Comprehensive Income (Reclassification out of AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment securities gains, net	$ 721	$ 223
Compensation and employee benefits	39,100	31,338
Total before tax	35,188	28,640
Income tax provision	(10,827)	(8,796)
Net of tax	24,361	19,844
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	721	223
Total before tax	721	223
Income tax provision	(262)	(81)
Net of tax	459	142
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	(44)	(37)
Total before tax	(44)	(37)
Income tax provision	16	13
Net of tax	$ (28)	$ (24)