Marketable Securities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, gross unrealized gains	$ 2.3	$ 3.6
Available-for-sale marketable securities, accumulated gross unrealized losses	1.5	1.6
Net gains on marketable securities	1.3	4.2	3.2
Noncurrent Auction Rate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Auction rate securities	6.7	6.3
Marketable Securities With No OTTI Incurred [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, accumulated gross unrealized losses	$ 1.5	$ 1.6