Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			$ (32,616)
Personnel expense	$ (102,129)	$ (102,986)	(203,527)	$ (203,138)
Interest income (Amortization of net unrealized gains on available for sale securities transferred to held to maturity securities)	(1,452)	0	(3,024)	0
Total other comprehensive income (loss)	(11,286)	22,206	(46,069)	(7,444)
Ending Balance	13,453		13,453
Investment Securities Available For Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	34,936	47,825	459	18,512
Other comprehensive income (loss) before reclassifications	22,321	(35,224)	82,743	12,194
Investment securities gain, net	(3,116)	(1,242)	(6,214)	(1,242)
Personnel expense	0	0	0	0
Interest income (Amortization of net unrealized gains on available for sale securities transferred to held to maturity securities)	(1,452)		(3,024)
Income tax (expense) benefit	(6,773)	13,923	(28,048)	(4,182)
Total other comprehensive income (loss)	(10,980)	22,543	(45,457)	(6,770)
Ending Balance	45,916	25,282	45,916	25,282
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(32,769)	(23,025)	(33,075)	(23,362)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Investment securities gain, net	0	0	0	0
Personnel expense	495	545	990	1,090
Interest income (Amortization of net unrealized gains on available for sale securities transferred to held to maturity securities)	0		0
Income tax (expense) benefit	(189)	(208)	(378)	(416)
Total other comprehensive income (loss)	(306)	(337)	(612)	(674)
Ending Balance	(32,463)	(22,688)	(32,463)	(22,688)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	2,167	24,800	(32,616)	(4,850)
Other comprehensive income (loss) before reclassifications	22,321	(35,224)	82,743	12,194
Investment securities gain, net	(3,116)	(1,242)	(6,214)	(1,242)
Personnel expense	495	545	990	1,090
Interest income (Amortization of net unrealized gains on available for sale securities transferred to held to maturity securities)	(1,452)		(3,024)
Income tax (expense) benefit	(6,962)	13,715	(28,426)	(4,598)
Total other comprehensive income (loss)	(11,286)	22,206	(46,069)	(7,444)
Ending Balance	$ 13,453	$ 2,594	$ 13,453	$ 2,594