Investments (Maturities Of Marketable Securities And Restricted Investments) (Details) (USD $) In Thousands	Sep. 30, 2011
Marketable Securities [Member]
Less than one year, Amortized Cost	$ 120,284
Due in year two through year three, Amortized Cost	307,669
Due in year four through year five, Amortized Cost	47,776
Due after five years, Amortized Cost	21,073
Total Amortized Cost	496,802
Less than one year, Fair Value	121,534
Due in year two through year three, Fair Value	310,586
Due in year four through year five, Fair Value	48,644
Due after five years, Fair Value	21,373
Total Fair Value	502,137
Restricted Investments [Member]
Less than one year, Amortized Cost	34,628
Due in year two through year three, Amortized Cost	40,719
Due in year four through year five, Amortized Cost	4,182
Due after five years, Amortized Cost	188
Total Amortized Cost	79,717
Less than one year, Fair Value	34,715
Due in year two through year three, Fair Value	40,876
Due in year four through year five, Fair Value	4,140
Due after five years, Fair Value	190
Total Fair Value	$ 79,921