Investment in Joint Venture (Narrative) (Details) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended			0 Months Ended	12 Months Ended				1 Months Ended
	Jul. 04, 2010	Oct. 01, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jul. 04, 2010 Apex	Dec. 31, 2012 Apex	Dec. 31, 2011 Apex	Dec. 31, 2010 Apex	Dec. 31, 2009 Apex	Feb. 21, 2013 Apex Subsequent Event
Sales of contributed business					$ 316,000,000					$ 1,200,000,000
Ownership in limited liability company						50.00%
Term debt financing						45,000,000
Receivables from the formation of joint venture						45,000,000
After-tax gain on contribution to joint venture	232,200,000	232,200,000
Gain from joint venture per diluted share		$ 0.34
Earnings from unconsolidated joint venture			69,900,000	66,800,000	22,800,000		70,000,000	67,000,000	23,000,000
Operating profit of contributed business					42,000,000
Proceeds from sale of equity method investments											1,600,000,000
Equity method investment, net sales proceeds											650,000,000
Equity method investment, after tax gain on sale											$ 138,000,000
Equity method investment, after tax gain on sale per diluted share											$ 0.19