Short-term Investments (Estimated Fair Value Of Short-Term Investments By Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Short-Term Investments And Fair Value Measurement [Abstract]
Due within one year	$ 128,506
Due after one year and through 5 years	519,446
Due after 5 years and through 10 years	4,015
Due after 10 years	43,964
Total short-term investments	$ 695,931