Accumulated Other Comprehensive Income (Reclassification out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment securities gains, net	$ 0	$ 373
Compensation and employee benefits	40,825	36,319
Total before tax	39,773	30,488
Income tax provision	(10,574)	(9,229)
Net income	29,199	21,259
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	373
Total before tax	0	373
Income tax provision	0	(135)
Net income	0	238
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	(136)	(167)
Total before tax	(136)	(167)
Income tax provision	49	61
Net income	$ (87)	$ (106)