Marketable Securities and Investments (Schedule of Activity of Major Classes of Assets Measured at Fair Value Using Level 3 Inputs) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ 254,119
Redemptions of securities		(124,100)
Unrealized gains included in accumulated other comprehensive income (loss), net		7,237
Realized gain on auction rate securities included in the statement of operations		9,614
Realized loss on other investment-related assets included in the statement of operations		(9,614)
Ending balance		137,256
Put Option Related to Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		9,614
Redemptions of securities		0
Unrealized gains included in accumulated other comprehensive income (loss), net		0
Realized gain on auction rate securities included in the statement of operations		0
Realized loss on other investment-related assets included in the statement of operations		(9,614)
Ending balance		0
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	137,256	244,505
Redemptions of securities	(137,256)	(124,100)
Unrealized gains included in accumulated other comprehensive income (loss), net		7,237
Realized gain on auction rate securities included in the statement of operations		9,614
Realized loss on other investment-related assets included in the statement of operations		0
Ending balance	$ 0	$ 137,256