Fair Value Measurements Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	$ 912,149	$ 892,119
Gross unrealized gains	1,248	1,366
Gross unrealized losses	(366)	(234)
Available-for-sale securities	913,031	893,251
Short-term marketable securities	340,005	235,592
Long-term marketable securities	573,026	657,659
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	222	3,100
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Available-for-sale securities	222	3,100
Short-term marketable securities	173	3,057
Long-term marketable securities	49	43
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost		7,481
Gross unrealized gains		2
Gross unrealized losses		(1)
Available-for-sale securities		7,482
Short-term marketable securities		7,482
Long-term marketable securities		0
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	736,945	691,931
Gross unrealized gains	1,197	1,269
Gross unrealized losses	(281)	(205)
Available-for-sale securities	737,861	692,995
Short-term marketable securities	278,318	217,548
Long-term marketable securities	459,543	475,447
U.S. government agency obligations
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	174,982	189,607
Gross unrealized gains	51	95
Gross unrealized losses	(85)	(28)
Available-for-sale securities	174,948	189,674
Short-term marketable securities	61,514	7,505
Long-term marketable securities	$ 113,434	$ 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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