Marketable Investment Securities, Restricted Cash and Cash Equivalents, and Other Investment (Details 4) (USD $)	Mar. 31, 2012	Dec. 31, 2011
Fair value of marketable investment securities in a loss position
Total	$ 720,569,000	$ 1,040,122,000
Unrealized loss on marketable investment securities in a loss position
Total	63,693,000	82,985,000
Debt securities
Fair value of marketable investment securities in a loss position
Less than 12 Months	439,812,000	694,199,000
12 Months or More	61,872,000	98,240,000
Unrealized loss on marketable investment securities in a loss position
Less than 12 Months	(796,000)	(4,793,000)
12 Months or More	(11,084,000)	(16,258,000)
Equity securities
Fair value of marketable investment securities in a loss position
Less than 12 Months	218,885,000	247,683,000
Unrealized loss on marketable investment securities in a loss position
Less than 12 Months	$ (51,813,000)	$ (61,934,000)