Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Benefit Plans (Textuals)
Contributions to qualified and non qualified pension plans			$ 14,915	$ 22,503
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	2,862	2,713	8,585	8,139
Interest cost	7,957	7,873	23,873	23,617
Expected return on plan assets	(10,205)	(10,183)	(30,616)	(30,550)
Amortization of prior service cost (benefit)	65	65	194	194
Recognized net actuarial loss	4,207	2,349	12,601	7,149
Net periodic pension benefit cost	4,886	2,817	14,637	8,549
Other Benefits [Member]
Components of net periodic benefit cost
Service cost	0	0	0	0
Interest cost	204	233	611	698
Expected return on plan assets	0	0	0	0
Amortization of prior service cost (benefit)	(130)	(130)	(388)	(388)
Recognized net actuarial loss	123	98	366	292
Net periodic pension benefit cost	$ 197	$ 201	$ 589	$ 602