Short-term Investments (Contractual Maturities Of Investments In Debt Securities Available-For-Sale) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014
Amortized Cost
Due within one year	$ 188,349
Due after one year up to two years	526,575
Due after two years up to three years	519,035
Due after three years up to four years	28,428
Asset-backed securities	228,298
Amortized Cost	1,490,685
Fair Value
Due within one year	188,543
Due after one year up to two years	527,250
Due after two years up to three years	518,719
Due after three years up to four years	28,400
Asset-backed securities	228,019
Fair Value	$ 1,490,931