Other Comprehensive Income/Loss (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Income before income tax expense	$ 24,560	$ 20,021	$ 46,193	$ 35,583
Income tax effect	8,895	7,197	16,676	12,763
Total reclassifications, net of tax	15,665	12,824	29,517	22,820
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	(1,166)		(146)
Income tax effect	411		52
Total reclassifications, net of tax	(755)		(94)
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)		(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	838		1,805
Reclassification adjustment for prior service cost	$ 53		$ 106