Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	$ 0		$ 0
Benefit Plans (Textuals)
Contributions to qualified and non qualified pension plans			1,597		13,780
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	3,330	2,861	6,661		5,723
Interest cost	6,956	7,958	13,913		15,916
Expected return on plan assets	(8,802)	(10,206)	(17,605)		(20,411)
Amortization of prior service cost (benefit)	19	64	37		129
Recognized net actuarial loss	5,435	4,183	10,856		8,394
Curtailment loss (1)			1,159	[1]	0	[1]
Net periodic pension benefit cost	6,938	4,860	15,021		9,751
Other Benefits [Member]
Components of net periodic benefit cost
Service cost	0	0	0		0
Interest cost	157	203	314		407
Expected return on plan assets	0	0	0		0
Amortization of prior service cost (benefit)	(122)	(129)	(244)		(258)
Recognized net actuarial loss	105	122	211		243
Curtailment loss (1)			0	[1]	0	[1]
Net periodic pension benefit cost	$ 140	$ 196	$ 281		$ 392

[1] The curtailment loss during the six months ended June 30, 2013 resulted from the departure of certain executive officers and was recorded within selling and administrative expense.