Pension Benefit and Retirement Health and Life Insurance Benefits (Assets Carried at Fair Value by Level) (Details) (Pension Benefits [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	$ 143,540	$ 120,565	$ 125,261
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	98,269	75,227
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	29,869	32,072
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	15,402	13,266
Estimate of Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	143,540	120,565
Pooled separate accounts [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	29,869	32,072
Pooled separate accounts [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	0
Pooled separate accounts [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	29,869	32,072
Pooled separate accounts [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	0
Pooled separate accounts [Member] | Estimate of Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	29,869	32,072
Mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	98,269	47,255
Mutual funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	98,269	47,255
Mutual funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	0
Mutual funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	0
Mutual funds [Member] | Estimate of Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	98,269	47,255
Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	27,804
Common Stock [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	27,804
Common Stock [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	0
Common Stock [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	0
Common Stock [Member] | Estimate of Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	27,804
Guaranteed deposit account [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	15,402	13,266
Guaranteed deposit account [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	0
Guaranteed deposit account [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	0
Guaranteed deposit account [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	15,402	13,266
Guaranteed deposit account [Member] | Estimate of Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	15,402	13,266
Interest bearing cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	168
Interest bearing cash [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	168
Interest bearing cash [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	0
Interest bearing cash [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	0	0
Interest bearing cash [Member] | Estimate of Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets at fair value	$ 0	$ 168