Other Comprehensive Income/Loss (Amounts Reclassified From Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Reclassification adjustment for gain on sales of securities included in net income, before tax amount	$ (72)		$ (72)
Reclassification adjustment for net actuarial loss	729	$ 249	1,486	$ 457
Reclassification adjustment for prior service cost	48	48	95	95
Income before income tax expense	31,583	33,768	60,468	63,553
Income tax effect	(152)	(11,468)	(9,730)	(9,704)
Net income	31,431	22,300	50,738	53,849
Amount Reclassified from Accumulated Other Comprehensive Loss
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Income before income tax expense	(705)	(297)	(1,509)	(552)
Income tax effect	304	105	610	195
Net income	(401)	(192)	(899)	(357)
Net unrealized (loss) gain on securities available-for-sale | Amount Reclassified from Accumulated Other Comprehensive Loss
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Reclassification adjustment for gain on sales of securities included in net income, before tax amount	72		72
Compensation and benefits | Amount Reclassified from Accumulated Other Comprehensive Loss
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Reclassification adjustment for net actuarial loss	(729)	(249)	(1,486)	(457)
Reclassification adjustment for prior service cost	$ (48)	$ (48)	$ (95)	$ (95)