Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ (32,616)
Personnel expense	(414,837)	$ (404,741)	$ (390,399)
Interest income	(5,887)	(555)	0
Total other comprehensive income (loss)	(22,063)	(27,766)	19,394
Ending Balance	(54,679)	(32,616)
Investments Securities Available For Sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	459	18,512	(11,396)
Other comprehensive income (loss) before reclassifications	(17,900)	(20,439)	49,038
Investment securities gain, net	(9,316)	(8,133)	(494)
Personnel expense	0	0	0
Interest income	(5,887)	(555)
Income tax (expense) benefit	12,565	11,074	(18,636)
Total other comprehensive income (loss)	(20,538)	(18,053)	29,908
Ending Balance	(20,079)	459	18,512
Defined Benefit Pension and Postretirement Obligations
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(33,075)	(23,362)	(12,848)
Other comprehensive income (loss) before reclassifications	(6,141)	(17,892)	(18,428)
Investment securities gain, net	0	0	0
Personnel expense	3,801	2,306	1,407
Interest income	0	0
Income tax (expense) benefit	815	5,873	6,507
Total other comprehensive income (loss)	(1,525)	(9,713)	(10,514)
Ending Balance	(34,600)	(33,075)	(23,362)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(32,616)	(4,850)	(24,244)
Other comprehensive income (loss) before reclassifications	(24,041)	(38,331)	30,610
Investment securities gain, net	(9,316)	(8,133)	(494)
Personnel expense	3,801	2,306	1,407
Interest income	(5,887)	(555)
Income tax (expense) benefit	13,380	16,947	(12,129)
Total other comprehensive income (loss)	(22,063)	(27,766)	19,394
Ending Balance	$ (54,679)	$ (32,616)	$ (4,850)