Subsequent Event (Details) (Amendment to 2011 Credit Agreement, 2011 Credit Agreement, USD $)	0 Months Ended
	Oct. 29, 2012
Subsequent Event
Increase in interest margin once the minimum senior unsecured notes aggregate principal amount not incurred (as a percent)	0.25%
Minimum aggregate principal amount requirement for increase in interest margin by 0.25%	$ 500,000,000
Total leverage ratio requirement for permitted acquisitions and unlimited unsecured debt (as a percent)	4.50
Increase in maximum availability if minimum percentage of proceeds from any offering are used to repay the term loans	1,000,000,000
Minimum percentage of proceeds from offering requirement for flexibiltiy to incur additional borrwoings of senior unsecured notes (as a percent)	50.00%
Minimum aggregate principal amount of senior unsecured notes, requirement for change in covenant	$ 500,000,000
Low end of range
Subsequent Event
Increase in interest margin from existing levels (as a percent)	1.25%
High end of range
Subsequent Event
Increase in interest margin from existing levels (as a percent)	1.50%