Other Comprehensive Income/Loss - Amounts Reclassified from Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Gain on sales of securities	$ 72	$ 141	$ 2,057
Compensation and benefits	(152,924)	(138,177)	(133,689)
Total reclassifications, before tax	117,874	122,195	104,342
Income tax effect	(29,799)	(26,279)	(37,749)
Net income	88,075	95,916	$ 66,593
Amount reclassified from accumulated other comprehensive income
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Total reclassifications, before tax	(3,091)	(962)
Income tax effect	1,250	339
Net income	(1,841)	(623)
Reclassification adjustment for 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
Gain on sales of securities	72	141
Reclassification adjustment for net actuarial loss | Amount reclassified from accumulated other comprehensive income
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Compensation and benefits	(2,973)	(913)
Reclassification adjustment for prior service cost | Amount reclassified from accumulated other comprehensive income
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Compensation and benefits	$ (190)	$ (190)