Stockholder's Equity (Details 1) (USD $)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Summary of common stock issuances
Public issuance, Shares Issued	16,100,000	23,000,000
Public issuance, Average Price	$ 62.35	$ 73.5
Public issuance, Gross Proceeds	$ 1,003,835,000	$ 1,690,500,000
Public issuance, Net Proceeds	968,517,000	1,630,636,000
Dividend reinvestment plan issuances, Shares Issued	2,132,427	1,370,661
Dividend reinvestment plan issuances, Average Price	58.73	66.87
Dividend reinvestment plan issuances, Net Proceeds	125,232,000	91,651,000
Dividend reinvestment plan issuances, Gross Proceeds	125,232,000	91,651,000
Option exercises, Shares	175,699	186,404
Option exercises, Average Price	46.78	42.64
Option exercises, Gross Proceeds	8,220,000	7,948,000
Option exercises, Net Proceeds	8,220,000	7,948,000
Stock incentive plans, net of forfeitures, Shares Issued	124,723	301,544
Issuance of Common Stock, Shares	18,766,086	24,858,627
Preferred stock conversions	233,236	0
Senior note conversions	1	18
Gross Proceeds From Issuance of Common Stock	1,137,287,000	1,790,099,000
Net proceeds from the issuance of common stock	$ 1,101,969,000	$ 1,730,235,000