PROPERTY AND EQUIPMENT Acquisitions and Disposals (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Significant Acquisitions and Disposals [Line Items]
Property, Plant and Equipment, Transfers and Changes		$ 2.6
Gross book value of fixed assets written off	7.3	26.0	8.0
Annual Depreciation	19.5	19.4	18.2
Former Corporate Headquarters [Member]
Significant Acquisitions and Disposals [Line Items]
Gross book value of fixed assets written off		22.7
Net book value of assets written off		0.1
Burlington, Massachusetts Corporate Headquarters [Member]
Significant Acquisitions and Disposals [Line Items]
Property, Plant and Equipment, Additions		31.7
Fixed asset additions		31.7
Non-cash addition to fixed assets included above		$ 6.0