Property And Equipment (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense of property and equipment	$ 39,800,000	$ 37,500,000	$ 35,100,000
Asset balance, gross	478,309,000	422,350,000
Existing Westbrook Facility [Member]
Property, Plant and Equipment [Line Items]
Current year additions		7,900,000
Asset balance, gross		82,200,000
New Westbrook Administrative Facility [Member]
Property, Plant and Equipment [Line Items]
Current year additions	13,900,000	3,400,000
Software Developed For Internal Use [Member]
Property, Plant and Equipment [Line Items]
Current year additions	$ 12,400,000	$ 5,700,000	$ 7,800,000