CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	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	1,021,306			1,021,306
Other comprehensive income (loss)	(1,864)				(1,864)
Dividends declared on common stock	(608,331)			(608,331)
Issuances of common stock (in shares)		7,761,000
Issuances of common stock	204,549	$ 19,404	185,145
Share-based compensation	32,872		32,872
Ending 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		505,733,000
Increase (Decrease) in Stockholders' Equity
Net income	984,485			984,485
Other comprehensive income (loss)	(1,614)				(1,614)
Dividends declared on common stock	(652,715)			(652,715)
Issuances of common stock (in shares)		1,803,000
Issuances of common stock	32,523	$ 4,506	28,017
Share-based compensation	23,759		23,759
Ending balance at Dec. 31, 2015	$ 10,600,920	$ 1,268,839	5,889,106	3,552,728	(109,753)
Balance (in shares) at Dec. 31, 2015	507,535,523	507,536,000
Increase (Decrease) in Stockholders' Equity
Net income	$ 1,123,379			1,123,379
Other comprehensive income (loss)	(601)				(601)
Dividends declared on common stock	(694,886)			(694,886)
Issuances of common stock (in shares)		486,000
Issuances of common stock	16,326	$ 1,216	15,110
Repurchases of common stock (in shares)		(799,000)
Repurchases of common stock	(32,209)	$ (1,998)	(30,211)
Share-based compensation	7,920		7,489	431
Ending balance at Dec. 31, 2016	$ 11,020,849	$ 1,268,057	$ 5,881,494	$ 3,981,652	$ (110,354)
Balance (in shares) at Dec. 31, 2016	507,222,795	507,223,000