Pension Benefit and Retirement Health and Life Insurance Benefits (Components of Net Periodic Benefit Cost) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Expected return of plan assets	$ (0.086)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4,596,000	3,922,000	3,563,000
Interest cost	8,420,000	8,535,000	8,345,000
Expected return of plan assets	(9,892,000)	(10,559,000)	(9,628,000)
Amortization of prior service cost	463,000	597,000	600,000
Amortization of net loss	5,471,000	2,331,000	1,824,000
Settlement charge/(credit)	2,073,000	0	372,000
Special termination benefit	0	176,000	0
Net periodic benefit cost	11,131,000	5,002,000	5,076,000
Retirement Health and Life Insurance Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	630,000	693,000	661,000
Interest cost	364,000	413,000	398,000
Expected return of plan assets	0	0	0
Amortization of prior service cost	(451,000)	(627,000)	(626,000)
Amortization of net loss	313,000	421,000	329,000
Settlement charge/(credit)	0	0	0
Special termination benefit	1,592,000	0	0
Net periodic benefit cost	$ 2,448,000	$ 900,000	$ 762,000