Fair Value Measurements Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	$ 951,153	$ 892,119
Gross unrealized gains	1,062	1,366
Gross unrealized losses	(711)	(234)
Aggregate fair value	951,504	893,251
Short-term marketable securities	331,300	235,592
Long-term marketable securities	620,204	657,659
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	219	3,100
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Aggregate fair value	219	3,100
Short-term marketable securities	171	3,057
Long-term marketable securities	48	43
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost		7,481
Gross unrealized gains		2
Gross unrealized losses		(1)
Aggregate fair value		7,482
Short-term marketable securities		7,482
Long-term marketable securities		0
U.S. Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	755,548	691,931
Gross unrealized gains	1,017	1,269
Gross unrealized losses	(514)	(205)
Aggregate fair value	756,051	692,995
Short-term marketable securities	296,783	217,548
Long-term marketable securities	459,268	475,447
U.S. Government Agencies Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	195,386	189,607
Gross unrealized gains	45	95
Gross unrealized losses	(197)	(28)
Aggregate fair value	195,234	189,674
Short-term marketable securities	34,346	7,505
Long-term marketable securities	$ 160,888	$ 182,169

- Definition

Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

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