Cash and Cash Equivalents and Investments in Marketable Securities (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Interest income	$ 5,556	$ 4,786	$ 1,284
Marketable securities
Schedule of Available-for-sale Securities [Line Items]
Interest income	$ 2,100	$ 1,100