Stockholders' Equity (Dividends Declared on Common Stock) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended						6 Months Ended		9 Months Ended
	Sep. 08, 2012	Jun. 16, 2012	Mar. 24, 2012	Sep. 10, 2011	Jun. 18, 2011	Mar. 26, 2011	Jun. 16, 2012	Jun. 18, 2011	Sep. 08, 2012	Sep. 10, 2011
Date Declared	Aug. 22, 2012	May 15, 2012	Mar. 16, 2012	Aug. 24, 2011	May 19, 2011	Mar. 15, 2011
Per-Share Amounts	$ 0.175	$ 0.175	$ 0.145	$ 0.145	$ 0.145	$ 0.120
Total	$ 41.9	$ 41.9	$ 36.3	$ 49.3	$ 50.7	$ 43.8	$ 78.2	$ 94.5	$ 120.1	$ 143.8
Dividends Declared On Common Stock Member
Record Date	Sep. 20, 2012	Jun. 21, 2012	Mar. 29, 2012	Sep. 22, 2011	Jun. 23, 2011	Mar. 24, 2011