Employee Benefits (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Pension Plan [Member]
Net periodic benefit cost
Service cost	$ 1,278,000	$ 870,000	$ 2,069,000	$ 1,583,000
Interest cost	1,334,000	1,237,000	2,524,000	2,380,000
Expected return on plan assets	(1,360,000)	(1,512,000)	(2,682,000)	(2,644,000)
Amortization of prior service cost	0	3,000	3,000	6,000
Amortization of net loss	1,684,000	639,000	2,276,000	1,184,000
Net periodic benefit cost	2,936,000	1,237,000	4,190,000	2,509,000
2012 Pension Plan Contribution Estimated and Disclosed in Prior Year 10K					7,000,000
Contribution by Employer			3,300,000
Postretirement Benefit Plan [Member]
Net periodic benefit cost
Service cost	496,000	614,000	992,000	993,000
Interest cost	398,000	439,000	796,000	795,000
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	(8,000)	(2,000)	(17,000)	(16,000)
Amortization of net loss	56,000	92,000	112,000	112,000
Net periodic benefit cost	$ 942,000	$ 1,143,000	$ 1,883,000	$ 1,884,000