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, 2013	$ 9,565,950	$ 1,244,929	$ 5,619,313	$ 2,807,983	$ (106,275)
Balance (in shares) at Dec. 31, 2013		497,972,000
Increase (Decrease) in Stockholders' Equity
Net income	261,221			261,221
Other comprehensive income	1,455				1,455
Dividends declared on common stock	(150,989)			(150,989)
Issuances of common stock	63,722	7,950	55,772
Issuances of common stock (in shares)		3,180,000
Share-based compensation	6,065		6,065
Ending balance at Mar. 31, 2014	9,747,424	1,252,879	5,681,150	2,918,215	(104,820)
Balance (in shares) at Mar. 31, 2014		501,152,000
Beginning balance at Dec. 31, 2014	10,214,482	1,264,333	5,837,330	3,220,958	(108,139)
Balance (in shares) at Dec. 31, 2014	505,733,267	505,733,000
Increase (Decrease) in Stockholders' Equity
Net income	152,066			152,066
Other comprehensive income	1,451				1,451
Dividends declared on common stock	(163,120)			(163,120)
Issuances of common stock	3,219	2,326	893
Issuances of common stock (in shares)		931,000
Share-based compensation	6,772		6,772
Ending balance at Mar. 31, 2015	$ 10,214,870	$ 1,266,659	$ 5,844,995	$ 3,209,904	$ (106,688)
Balance (in shares) at Mar. 31, 2015	506,663,770	506,664,000