Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012
Amortized cost and estimated fair value of marketable debt securities
Amortized Cost Due in one year or less	$ 1,502,255
Amortized Cost Due after one year through five years	303,951
Amortized Cost Due after five years through ten years	253,312
Amortized Cost Due after ten years	785,970
Amortized Cost Total	2,845,488
Estimated Fair Value Due in one year or less	1,502,405
Estimated Fair Value Due after one year through five years	308,085
Estimated Fair Value Due after five years through ten years	257,837
Estimated Fair Value Due after ten years	793,521
Estimated Fair Value Total	$ 2,861,848