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Comprehensive Income (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				$ (9,425)					$ (9,425)
Other Comprehensive Income Loss Reclassification Adjustment From AOCI For Non Credit Other Than Temporary Impaired Securities Net Of Tax									(138)	$ (232)	$ (1,085)
Amount reclassified from AOCI, HTM									92	377	844
OCI before reclassifications, Defined Benefit Pension and Post Retirement Plans									(7,852)	1,585	(35,189)
Amounts reclassified from AOCI,All other									3,064	(9,110)	(18,762)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax									(3,652)	6,185	(33,953)
Other comprehensive loss	$ (78,159)	$ (9,798)	$ 36,010	45,422	$ (3,386)	$ 6,290	$ (35,944)	$ 3,827	(6,525)	(29,213)	(5,063)
Balance December,	(15,950)				(9,425)				(15,950)	(9,425)
Accumulated Other-than-Temporary Impairment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				(282)				(514)	(282)	(514)
OCI before reclassifications									(6)	0
Other comprehensive loss									132	232
Balance December,	(150)				(282)				(150)	(282)	(514)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				(54,420)				(60,605)	(54,420)	(60,605)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax									4,200	4,600
Balance December,	(58,072)				(54,420)				(58,072)	(54,420)	(60,605)
Accumulated other comprehensive income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				(9,425)				19,788	(9,425)	19,788
OCI before reclassifications									(13,835)	(24,558)
Amount reclassified from AOCI									7,310	(4,655)
Other comprehensive loss									(6,525)	(29,213)	(5,063)
Balance December,	(15,950)				(9,425)				(15,950)	(9,425)	19,788
Held-to-maturity Securities [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				194				623	194	623
OCI before reclassifications									0	(52)
Other comprehensive loss									(92)	(429)
Balance December,	102				194				102	194	623
Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				45,083				80,284	45,083	80,284
OCI before reclassifications									(5,977)	(26,091)
Other comprehensive loss									(2,913)	(35,201)
Balance December,	42,170				45,083				42,170	45,083	80,284
Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				$ 44,995				$ 80,393	44,995	80,393
OCI before reclassifications									(5,983)	(26,143)
Amount reclassified from AOCI									3,110	(9,255)
Other comprehensive loss									(2,873)	(35,398)
Balance December,	$ 42,122				$ 44,995				$ 42,122	$ 44,995	$ 80,393

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Net of tax amount of the reclassification adjustment related to held-to-maturity securities transferred from the available-for-sale category. This amount includes amortization and amounts realized from the disposal of these securities.

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