Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years customers	Dec. 31, 2010 customers	Dec. 31, 2009 customers
Summary of Significant Accounting Policies [Abstract]
Number of customers accounted for 10% or more of total revenues	0	0	0
Customer revenue as percentage of total revenue, Minimum	10.00%
Number of customers related to greater than 10% of accounts receivable	1	1
Customer account receivable balance as percentage of total account receivable, minimum	10.00%	10.00%
Minimum percentage of tax benefit to be recognized	50.00%
Unrecognized tax benefits including accrued interest and penalties	$ 17.2	$ 15.1
Foreign currency transaction gain (loss)	1.9	2.5	1.7
Cash and cash equivalents and marketable securities	1,230.0	1,243.4
Property and equipment per unit value, minimum (in whole number)	1,000
Property, plant and equipment, useful life, minimum (in years)	1
Advertising expense	$ 0.8	$ 0.5	$ 0.7