Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ (4,850)
Personnel expense	(404,741)	$ (390,399)	$ (397,015)
Total other comprehensive income (loss)	(27,766)	19,394	(72,847)
Ending Balance	(32,616)	(4,850)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(4,850)	(24,244)	48,603
Other comprehensive income (loss) before reclassifications	(38,331)	30,610	(122,403)
Amounts reclassified from accumulated other comprehensive income (loss):	(8,133)	(494)	(564)
Personnel expense	2,306	1,407	4,416
Interest income	(555)
Income tax (expense) benefit	16,947	(12,129)	45,704
Total other comprehensive income (loss)	(27,766)	19,394	(72,847)
Ending Balance	(32,616)	(4,850)	(24,244)
Investment Securities Available For Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	18,512	(11,396)	86,109
Other comprehensive income (loss) before reclassifications	(20,439)	49,038	(158,207)
Amounts reclassified from accumulated other comprehensive income (loss):	(8,133)	(494)	(564)
Personnel expense	0	0	0
Interest income	(555)
Income tax (expense) benefit	11,074	(18,636)	61,266
Total other comprehensive income (loss)	(18,053)	29,908	(97,505)
Ending Balance	459	18,512	(11,396)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(23,362)	(12,848)	(37,506)
Other comprehensive income (loss) before reclassifications	(17,892)	(18,428)	35,804
Amounts reclassified from accumulated other comprehensive income (loss):	0	0	0
Personnel expense	2,306	1,407	4,416
Interest income	0
Income tax (expense) benefit	5,873	6,507	(15,562)
Total other comprehensive income (loss)	(9,713)	(10,514)	24,658
Ending Balance	$ (33,075)	$ (23,362)	$ (12,848)