Benefit Plans (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		1 Months Ended	9 Months Ended
	Sep. 30, 2011 Pension and Supplemental Executive Retirement Plans [Member]	Sep. 30, 2010 Pension and Supplemental Executive Retirement Plans [Member]	Sep. 30, 2011 Pension and Supplemental Executive Retirement Plans [Member]	Sep. 30, 2010 Pension and Supplemental Executive Retirement Plans [Member]	Sep. 30, 2011 Other Postretirement Benefits [Member]	Sep. 30, 2010 Other Postretirement Benefits [Member]	Sep. 30, 2011 Other Postretirement Benefits [Member]	Sep. 30, 2010 Other Postretirement Benefits [Member]	Nov. 30, 2011 Pension Plan [Member]	Sep. 30, 2011 Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 2,229,000	$ 2,133,000	$ 6,688,000	$ 6,399,000	$ 273,000	$ 281,000	$ 818,000	$ 844,000
Interest cost	4,025,000	3,885,000	12,074,000	11,652,000	338,000	295,000	1,013,000	887,000
Expected return on plan assets	(4,343,000)	(3,626,000)	(13,030,000)	(10,877,000)	(824,000)	(722,000)	(2,474,000)	(2,168,000)
Recognized net actuarial loss	1,002,000	1,481,000	3,008,000	4,443,000	157,000	191,000	473,000	573,000
Amortization of prior service cost	165,000	162,000	496,000	487,000	(1,554,000)	(1,534,000)	(4,663,000)	(4,603,000)
Net periodic benefit cost	3,078,000	4,035,000	9,236,000	12,104,000	(1,610,000)	(1,489,000)	(4,833,000)	(4,467,000)
Employer contributions during the period									$ 10,000,000	$ 10,000,000