Short-Term and Long-Term Marketable Securities (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Total available for sale short-term and long-term securities	$ 224,576,000	$ 49,737,000
Fair Value, Measurements, Recurring [Member] | Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	147,702,000	28,473,000
Gross Unrealized Gains	50,000	17,000
Gross Unrealized Losses	(12,000)	(5,000)
Total available for sale short-term and long-term securities	147,740,000	28,485,000
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32,439,000	18,767,000
Gross Unrealized Gains	16,000	7,000
Gross Unrealized Losses	(6,000)	(4,000)
Total available for sale short-term and long-term securities	32,449,000	18,770,000
Fair Value, Measurements, Recurring [Member] | Short-term Investments | U.S. dollar dominated foreign corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,728,000	5,060,000
Gross Unrealized Gains	5,000	9,000
Gross Unrealized Losses	(3,000)	(1,000)
Total available for sale short-term and long-term securities	15,730,000	5,068,000
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	57,906,000	4,646,000
Gross Unrealized Gains	16,000	1,000
Gross Unrealized Losses	(1,000)	0
Total available for sale short-term and long-term securities	57,921,000	4,647,000
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,150,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(1,000)
Total available for sale short-term and long-term securities	1,149,000
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	37,474,000
Gross Unrealized Gains	13,000
Gross Unrealized Losses	0
Total available for sale short-term and long-term securities	37,487,000	5,068,000
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,005,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(1,000)
Total available for sale short-term and long-term securities	3,004,000
Fair Value, Measurements, Recurring [Member] | Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	76,829,000	21,239,000
Gross Unrealized Gains	45,000	21,000
Gross Unrealized Losses	(38,000)	(8,000)
Total available for sale short-term and long-term securities	76,836,000	21,252,000
Fair Value, Measurements, Recurring [Member] | Long-term Investments | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,836,000	16,132,000
Gross Unrealized Gains	6,000	16,000
Gross Unrealized Losses	(20,000)	(7,000)
Total available for sale short-term and long-term securities	19,822,000	16,141,000
Fair Value, Measurements, Recurring [Member] | Long-term Investments | U.S. dollar dominated foreign corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,169,000	3,038,000
Gross Unrealized Gains	12,000	4,000
Gross Unrealized Losses	(2,000)	(1,000)
Total available for sale short-term and long-term securities	16,179,000	3,041,000
Fair Value, Measurements, Recurring [Member] | Long-term Investments | Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,252,000
Gross Unrealized Gains	17,000
Gross Unrealized Losses	(12,000)
Total available for sale short-term and long-term securities	14,257,000
Fair Value, Measurements, Recurring [Member] | Long-term Investments | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,148,000	2,069,000
Gross Unrealized Gains	5,000	1,000
Gross Unrealized Losses	0	0
Total available for sale short-term and long-term securities	6,153,000	2,070,000
Fair Value, Measurements, Recurring [Member] | Long-term Investments | Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,150,000
Gross Unrealized Gains	1,000
Gross Unrealized Losses	(4,000)
Total available for sale short-term and long-term securities	9,147,000
Fair Value, Measurements, Recurring [Member] | Long-term Investments | US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,274,000
Gross Unrealized Gains	4,000
Gross Unrealized Losses	0
Total available for sale short-term and long-term securities	$ 11,278,000