Cash and Cash Equivalents and Short-term Investments (Details 5) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Available-for-sale:
Proceeds from sales and maturities	$ 107,586	$ 24,010	$ 12,672
Realized gains (losses), net	$ 88,158	$ 13,405	$ 3,036