Employee 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
Qualified Pension [Member]
Schedule of net periodic benefit cost related to pension and post-retirement healthcare
Service cost	$ 4,638	$ 4,096	$ 9,276	$ 8,192
Interest cost	3,704	3,637	7,401	7,299
Expected return on plan assets	(3,132)	(3,252)	(6,302)	(6,531)
Amortization of actuarial loss	1,188	525	2,344	1,042
Plan Settlement	(1,014)	0	(1,014)	(356)
Net periodic benefit cost	7,412	5,006	13,733	10,358
Post-retirement Healthcare [Member]
Schedule of net periodic benefit cost related to pension and post-retirement healthcare
Service cost	7,482	6,784	14,964	13,568
Interest cost	6,493	6,183	12,986	12,365
Expected return on plan assets	0	(9)	0	(17)
Amortization of actuarial loss	2,235	1,682	4,470	3,364
Plan Settlement	0	0		0
Net periodic benefit cost	$ 16,210	$ 14,640	$ 32,420	$ 29,280