Accumulated Other Comprehensive Income (Reclassification out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment securities gains, net			$ 1,064	$ 519
Compensation and employee benefits	$ 38,446	$ 31,064	77,546	62,402
Total before tax	31,799	29,870	66,987	58,510
Income tax provision	(9,853)	(8,643)	(20,680)	(17,439)
Net of tax	21,946	21,227	46,307	41,071
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	343	296	1,064	519
Total before tax	343	296	1,064	519
Income tax provision	(124)	(107)	(386)	(188)
Net of tax	219	189	678	331
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	(98)	(37)	(142)	(74)
Total before tax	(98)	(37)	(142)	(74)
Income tax provision	35	13	51	26
Net of tax	$ (63)	$ (24)	$ (91)	$ (48)