Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			$ (54,679)
Personnel expense	$ (105,852)	$ (103,819)	(314,954)	$ (307,346)
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	76	(1,441)	(2,499)	(4,465)
Total other comprehensive income (loss)	(818)	(14,707)	391	31,362
Ending Balance	(54,288)		(54,288)
Investment Securities Available For Sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(19,428)	45,916	(20,079)	459
Other comprehensive income (loss) before reclassifications	(1,986)	(22,894)	1,646	59,849
Investment securities gain, net		13		(6,201)
Personnel expense	0	0	0	0
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	76	(1,441)	(2,499)	(4,465)
Income tax (expense) benefit	734	9,280	328	(18,768)
Total other comprehensive income (loss)	(1,176)	(15,042)	(525)	30,415
Ending Balance	(20,604)	30,874	(20,604)	30,874
Defined Benefit Pension and Post Retirement Obligations
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(34,042)	(32,463)	(34,600)	(33,075)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Investment securities gain, net		0		0
Personnel expense	583	541	1,483	1,531
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	0	0	0	0
Income tax (expense) benefit	(225)	(206)	(567)	(584)
Total other comprehensive income (loss)	358	335	916	947
Ending Balance	(33,684)	(32,128)	(33,684)	(32,128)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(53,470)	13,453	(54,679)	(32,616)
Other comprehensive income (loss) before reclassifications	(1,986)	(22,894)	1,646	59,849
Investment securities gain, net		13		(6,201)
Personnel expense	583	541	1,483	1,531
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	76	(1,441)	(2,499)	(4,465)
Income tax (expense) benefit	509	9,074	(239)	(19,352)
Total other comprehensive income (loss)	(818)	(14,707)	391	31,362
Ending Balance	$ (54,288)	$ (1,254)	$ (54,288)	$ (1,254)