Other Comprehensive Income/Loss (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Amounts reclassified from accumulated other comprehensive loss to the consolidated statements of income
Reclassification adjustment for net actuarial loss	$ 757	$ 208
Reclassification adjustment for prior service cost	47	47
Income before income tax expense (benefit)	28,885	29,785
Income tax effect	(9,578)	1,764
Net income	19,307	31,549
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 (benefit)	(804)	(255)
Income tax effect	306	90
Net income	(498)	(165)
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	(757)	(208)
Reclassification adjustment for prior service cost	$ (47)	$ (47)