Stockholders' Equity (Line Items in Consolidated Income Statements Affected by Amounts Reclassified from Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of defined benefit pension and post-retirement items		$ (14,004)	$ (12,870)	$ (29,718)	$ (28,504)
Tax effect		(13,618)	(12,311)	(14,733)	(27,187)
Net income		$ 46,907	$ 34,829	50,746	74,988
Amount Reclassified from Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	[1]			(2,129)	(1,920)
Amount Reclassified from Accumulated Other Comprehensive Income [Member] | Available for Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of AFS securities	[1]			1,114	165
Tax effect	[1]			(390)	(58)
Net income	[1]			724	107
Amount Reclassified from Accumulated Other Comprehensive Income [Member] | HTM Securities Transferred from AFS [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of unrealized net loss on securities transferred to HTM	[1]			(1,628)	(1,586)
Tax effect	[1]			625	580
Net income	[1]			(1,003)	(1,006)
Amount Reclassified from Accumulated Other Comprehensive Income [Member] | Employee Benefit Plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of defined benefit pension and post-retirement items	[1],[2]			(2,916)	(1,571)
Tax effect	[1]			1,066	550
Net income	[1]			$ (1,850)	$ (1,021)

[1] Amounts in parenthesis indicate reduction in net income.

[2] These accumulated other comprehensive income components are included in the computation of net periodic pension and post-retirement cost that is reported with employee benefits expense (see Note 11 for additional details).