Intangible Assets and Goodwill (Details 1) (USD $)	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2010
Summary of roll forward of the changes in goodwill
Goodwill, beginning of period	$ 1,146,314,000	$ 1,146,300,000
Goodwill acquired during the period	47,000,000
Goodwill, end of period	$ 1,193,279,000	$ 1,146,300,000