Stockholder's Equity (Details 1) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Summary of common stock issuances
Public issuance, Shares Issued	17,825,000	23,000,000
Public issuance, Average Price	$ 63.75	$ 73.5
Public issuance, Gross Proceeds	1,136,343,750	1,690,500,000
Public issuance, Net Proceeds	1,095,883,000	1,630,281,000
Dividend reinvestment plan issuances, Shares Issued	3,114,052	2,379,609
Dividend reinvestment plan issuances, Average Price	60.05	64.62
Dividend reinvestment plan issuances, Net Proceeds	186,996,000	153,762,000
Dividend reinvestment plan issuances, Gross Proceeds	186,996,000	153,762,000
Option exercises, Shares	207,046	200,467
Option exercises, Average Price	45.94	42.45
Option exercises, Gross Proceeds	9,512,000	8,509,000
Option exercises, Net Proceeds	9,512,000	8,509,000
Stock incentive plans, net of forfeitures, Shares Issued	186,837
Issuance of Common Stock, Shares	37,866,114	27,676,960
Preferred stock conversions	233,236	0
Senior note conversions	199,943	987,967
Equity issued in acquisition of noncontrolling interest		1,108,917
Gross Proceeds From Issuance of Common Stock	2,336,686,750	1,852,771,000
Net proceeds from the issuance of common stock	2,260,908,000	1,792,552,000
June 2014 Public Issuance [Member]
Summary of common stock issuances
Public issuance, Shares Issued	16,100,000
Public issuance, Average Price	62.35
Public issuance, Gross Proceeds	1,003,835,000
Public issuance, Net Proceeds	$ 968,517,000