Marketable Securities, Available-for-sale (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Contractual maturity:
ESTIMATED FAIR VALUE	$ 367,521	$ 385,625
Total debt securities
Contractual maturity:
Maturing in one year or less	130,674	66,546
Maturing after one year through three years	184,022	257,595
Maturing after three years	25,793	24,958
ESTIMATED FAIR VALUE	340,489	349,099
Time deposits and short-term pooled investments
Contractual maturity:
ESTIMATED FAIR VALUE	$ 27,032	$ 36,526