Equity (Details 1) (USD $) In Thousands, except Share data	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 28, 2011	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011		Sep. 30, 2010
Other comprehensive income and total comprehensive income
Consolidated net income		$ 633,069	$ 497,901	$ 1,207,346	[1]	$ 1,036,999	[1]
Other comprehensive income
Cash flow hedges net unrealized loss		(12,597)	53,840	(84,321)		112,911
Pension and other postretirement liabilities		2,657	1,001	9,255		6,011
Net unrealized investment gain (loss)		(53,349)	48,280	(25,478)		29,078
Foreign currency translation		108	510	419		(249)
Total comprehensive income		569,888	601,532	1,107,221		1,184,750
Equity (Textuals) [Abstract]
Treasury Stock issued				804,801
Common stock purchased				3,475,000
Common stock repurchases				(234,632)		(665,624)
Common stock dividend	$ 0.83	$ 0.83	$ 0.83	$ 2.49		$ 2.41
Net of tax benefit in cash flow hedges net unrealized loss		(9,041)	32,466	50,884		69,053
Net of tax expense in pension and other postretirement liabilities		1,647	2,236
Net of tax expense (benefit) net unrealized investment gains		(52,740)	44,499
Net of tax expense (benefit) in foreign currency translation		$ 59	$ 275	$ 226		$ 135

[1] Consolidated net income and preferred dividend requirements of subsidiaries for both 2010 and 2011 include $10.1 million of preferred dividends on subsidiaries' preferred stock without sinking fund that is not presented as equity.