Condensed Statements Of Income (Parenthetical) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Distributions declared	$ 2.60	[1]	$ 2.60	[2]	$ 7.35	[3]	$ 7.35	[4]
Dividends Declared, 9/12/2014 [Member]
Distributions declared	$ 2.60
Distributions date declared	Sep. 12, 2014
Distributions date payable	Oct. 31, 2014
Dividends Declared, 9/13/2013 [Member]
Distributions declared			$ 2.60
Distributions date declared			Sep. 13, 2013
Distributions date paid			Oct. 31, 2013
Dividends Declared, 3/14/2014 [Member]
Distributions declared					$ 2.25
Distributions date declared					Mar. 14, 2014
Distributions date paid					Apr. 30, 2014
Dividends Declared, 6/16/2014 [Member]
Distributions declared					$ 2.50
Distributions date declared					Jun. 16, 2014
Distributions date paid					Jul. 31, 2014
Dividends Declared, 9/12/2014 [Member]
Distributions declared					$ 2.60
Distributions date declared					Sep. 12, 2014
Distributions date payable					Oct. 31, 2014
Dividends Declared, 3/8/2013 [Member]
Distributions declared							$ 2.25
Distributions date declared							Mar. 08, 2013
Distributions date paid							Apr. 30, 2013
Dividends Declared, 6/17/2013 [Member]
Distributions declared							$ 2.50
Distributions date declared							Jun. 17, 2013
Distributions date paid							Jul. 31, 2013
Dividends Declared, 9/13/2013 [Member]
Distributions declared							$ 2.60
Distributions date declared							Sep. 13, 2013
Distributions date paid							Oct. 31, 2013

[1] $2.60 declared 9/12/2014 payable 10/31/2014

[2] $2.60 declared 9/13/2013 paid 10/31/2013

[3] $2.25 declared 3/14/2014 paid 4/30/2014 plus $2.50 declared 6/16/2014 payable 7/31/2014 plus $2.60 declared 9/12/2014 payable 10/31/2014

[4] $2.25 declared 3/8/2013 paid 4/30/2013 plus $2.50 declared 6/17/2013 paid 7/31/2013 plus $2.60 declared 9/13/2013 paid 10/31/2013