Acquisitions Acquisitions (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Business Combinations [Abstract]
Business Acquisition, Cost of Acquired Entity, Purchase Price	$ 37
Business Acquisition, Cost of Acquired Entity, Cash Paid	24
Business Acquisition, Contingent Consideration, at Fair Value	13
Business Acquisition, Purchase Price Allocation, Intangible Assets Other than Goodwill	21
Business Acquisition, Purchase Price Allocation, Goodwill Amount	$ 29