Equity (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011		Jun. 30, 2010
Other comprehensive income and total comprehensive income
Consolidated net income	$ 320,598	$ 320,283	$ 574,277	[1]	$ 539,097	[1]
Other comprehensive income
Cash flow hedges net unrealized loss	(13,516)	(83,467)	(71,724)		59,071
Pension and other postretirement liabilities (net of tax expense of $543)	(2,339)	(3,205)	(6,598)		(5,010)
Net unrealized investment gain (loss)	3,186	(36,043)	27,871		(19,202)
Foreign currency translation	11	(152)	311		(759)
Total comprehensive income	312,618	203,826	537,333		583,217
Equity (Textuals) [Abstract]
Treasury Stock issued			424,598
Common stock purchased			2,337,000
Common stock repurchases			(159,602)		(137,749)
Common stock dividend	$ 0.83	$ 0.83	$ 1.66		$ 1.58
Net of tax benefit in cash flow hedges net unrealized loss	7,208	50,672	(41,843)		36,587
Net of tax expense in pension and other postretirement liabilities	1,964	1,650
Net of tax expense (benefit) net unrealized investment gains	3,386	(33,891)
Net of tax expense (benefit) in foreign currency translation	$ 6	$ (82)	$ 167		$ (409)

[1] Consolidated net income and preferred dividend requirements of subsidiaries for both 2010 and 2011 include $6.6 million of preferred dividends on subsidiaries' preferred stock without sinking fund that is not presented as equity.