Other Comprehensive Income/Loss (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Reclassification adjustment for gain on sales of securities			$ (2,057)
Reclassification adjustment for net actuarial loss	903		2,708
Reclassification adjustment for prior service cost	53		159
Income before income tax expense	26,438	20,429	72,631	56,012
Income tax effect	(9,514)	(7,074)	(26,190)	(19,837)
Net income	16,924	13,355	46,441	36,175
Amount Reclassified from Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Income before income tax expense	(956)		(810)
Income tax effect	337		285
Net income	(619)		(525)
Gain on sales of securities | Amount Reclassified from Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Reclassification adjustment for gain on sales of securities			2,057
Compensation and benefits | Amount Reclassified from Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Reclassification adjustment for net actuarial loss	(903)		(2,708)
Reclassification adjustment for prior service cost	$ (53)		$ (159)