Benefit Plans (Details) (USD $)	1 Months Ended			12 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Apr. 30, 2011	Jul. 31, 2010	Mar. 31, 2010	Dec. 31, 2010	Jun. 30, 2011 Pension Benefits [Member]	Jun. 30, 2010 Pension Benefits [Member]	Jun. 30, 2011 Pension Benefits [Member]	Jun. 30, 2010 Pension Benefits [Member]	Jun. 30, 2011 Other Postretirement Benefits [Member]	Jun. 30, 2010 Other Postretirement Benefits [Member]	Jun. 30, 2011 Other Postretirement Benefits [Member]	Jun. 30, 2010 Other Postretirement Benefits [Member]	Dec. 31, 2008 Investment at Westridge Capital Management [Member]
Components of Net Periodic Benefit Cost
Service cost					$ 5,191,000	$ 4,800,000	$ 10,381,000	$ 9,608,000	$ 1,198,000	$ 1,067,000	$ 2,395,000	$ 2,133,000
Interest cost					10,650,000	10,406,000	21,192,000	20,811,000	1,612,000	1,662,000	3,225,000	3,325,000
Expected return on plan assets					(12,370,000)	(12,526,000)	(24,740,000)	(25,061,000)
Amortization of prior service cost					85,000	115,000	170,000	230,000	(168,000)	(182,000)	(337,000)	(364,000)
Amortization of actuarial loss					3,011,000	1,540,000	5,835,000	2,876,000	287,000	222,000	574,000	444,000
Net periodic pension benefit cost					6,567,000	4,335,000	12,838,000	8,464,000	2,929,000	2,769,000	5,857,000	5,538,000
Pretax reclassification from OCI included in net periodic benefit cost					3,096,000	1,655,000	6,005,000	3,106,000	119,000	40,000	237,000	80,000
Benefit Plans (Textuals)
Fair value of pension plan assets													59,245,000
Write-down in estimated fair value of assets													48,018,000
Total contributions (cash and stock) to qualified pension plans			72,500,000
Contributions to pension plans in cash			18,636,000
Contributions to pension plans in stock			53,864,000
Number of shares contributed to pension plans			1,190,000
Value per share of shares contributed to pension plans			$ 45.26
Additional contribution to pension plan		1,300,000
Partial distribution amount released by court-appointed receiver				6,555,000
Insurance settlement amount received by the Master Pension Trust related to the WCM loss				15,000,000
Additional distribution amount released by court-appointed receiver	$ 22,041,000