CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDERS' EQUITY (UNAUDITED) (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2012	$ 8,874,077	$ 1,219,899	$ 5,353,015	$ 2,413,816	$ (112,653)
Balance (in shares) at Dec. 31, 2012		487,960,000
Increase (Decrease) in Stockholders' Equity
Net income	798,179			798,179
Other comprehensive gain	2,673				2,673
Dividends declared on common stock	(414,509)			(414,509)
Issuances of common stock	252,916	24,165	228,751
Issuances of common stock (in shares)		9,666,000
Share-based compensation	33,950		33,950
Ending balance at Sep. 30, 2013	9,547,286	1,244,064	5,615,716	2,797,486	(109,980)
Balance (in shares) at Sep. 30, 2013		497,626,000
Beginning balance at Jun. 30, 2013	9,300,245	1,243,239	5,595,906	2,572,935	(111,835)
Balance (in shares) at Jun. 30, 2013		497,296,000
Increase (Decrease) in Stockholders' Equity
Net income	364,752			364,752
Other comprehensive gain	1,855				1,855
Dividends declared on common stock	(140,201)			(140,201)
Issuances of common stock	9,791	825	8,966
Issuances of common stock (in shares)		330,000
Share-based compensation	10,844		10,844
Ending balance at Sep. 30, 2013	9,547,286	1,244,064	5,615,716	2,797,486	(109,980)
Balance (in shares) at Sep. 30, 2013		497,626,000
Beginning balance at Dec. 31, 2013	9,565,950	1,244,929	5,619,313	2,807,983	(106,275)
Balance (in shares) at Dec. 31, 2013	497,971,508	497,972,000
Increase (Decrease) in Stockholders' Equity
Net income	824,967			824,967
Other comprehensive gain	4,274				4,274
Dividends declared on common stock	(455,563)			(455,563)
Issuances of common stock	194,591	18,631	175,960
Issuances of common stock (in shares)		7,452,000
Share-based compensation	20,441		20,441
Ending balance at Sep. 30, 2014	10,154,660	1,263,560	5,815,714	3,177,387	(102,001)
Balance (in shares) at Sep. 30, 2014	505,424,067	505,424,000
Beginning balance at Jun. 30, 2014	9,920,772	1,262,764	5,799,968	2,961,406	(103,366)
Balance (in shares) at Jun. 30, 2014		505,106,000
Increase (Decrease) in Stockholders' Equity
Net income	368,582			368,582
Other comprehensive gain	1,365				1,365
Dividends declared on common stock	(152,601)			(152,601)
Issuances of common stock	9,931	796	9,135
Issuances of common stock (in shares)		318,000
Share-based compensation	6,611		6,611
Ending balance at Sep. 30, 2014	$ 10,154,660	$ 1,263,560	$ 5,815,714	$ 3,177,387	$ (102,001)
Balance (in shares) at Sep. 30, 2014	505,424,067	505,424,000