Cash and Cash Equivalents and Short-term Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash and Cash Equivalents and Short-term Investments
Cash and cash equivalents	$ 389,915	$ 524,922	$ 398,575	$ 641,702
Short-term investments:
Trading equity securities		52,705
Available-for-sale equity securities	96,942	174,610
Available-for-sale debt securities	20,276	25,967
Total short-term investments	$ 117,218	$ 253,282