Cash and Cash Equivalents and Investments in Marketable Securities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Schedule of Available-for-sale Securities [Line Items]
Maximum term to maturity from date of purchase (years)	1 year
Total Marketable Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment Income, interest income on Marketable Securities	$ 0.6	$ 0.6	$ 1.2	$ 1.1