5. Cash, Cash Equivalents, Marketable Securities (Details) - Available For Sale (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 493,378,000	$ 439,621,000
Available-for-sale securities, gross unrealized gains	57,000	143,000
Available-for-sale Securities, Gross Unrealized Loss	560,000	662,000
Marketable securities	492,875,000	439,102,000
Available-for-sale Securities, Net Unrealized Gain (Loss)	(500,000)	(500,000)
Marketable securities, continuous unrealized loss position:
Marketable securities, in loss position for less than 12 months, estimated fair value	384,229,000	259,281,000
Marketable securities, in loss position for less than 12 months, gross unrealized losses	560,000	662,000
Marketable securities, in loss position for 12 months or greater, estimated fair value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	0	0
Marketable securities, in loss position, estimated fair value	384,229,000	259,281,000
Marketable securities, in loss position, gross unrealized losses	560,000	662,000
Available For Sale Securities Debt Maturities Within One Year [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	367,111,000	161,752,000
Available-for-sale securities, gross unrealized gains	44,000	57,000
Available-for-sale Securities, Gross Unrealized Loss	250,000	84,000
Marketable securities	366,905,000	161,725,000
Available For Sale Securities Debt Maturities Over One Year To Two Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	100,965,000	270,149,000
Available-for-sale securities, gross unrealized gains	13,000	81,000
Available-for-sale Securities, Gross Unrealized Loss	235,000	578,000
Marketable securities	100,743,000	269,652,000
Available For Sale Securities Debt Maturities Over Two Years To Three Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	25,302,000	7,720,000
Available-for-sale securities, gross unrealized gains	0	5,000
Available-for-sale Securities, Gross Unrealized Loss	75,000	0
Marketable securities	25,227,000	7,725,000
Federal Agency Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	6,803,000	46,430,000
Available-for-sale securities, gross unrealized gains	4,000	12,000
Available-for-sale Securities, Gross Unrealized Loss	0	3,000
Marketable securities	6,807,000	46,439,000
Marketable securities, continuous unrealized loss position:
Marketable securities, in loss position for less than 12 months, estimated fair value		21,465,000
Marketable securities, in loss position for less than 12 months, gross unrealized losses		3,000
Marketable securities, in loss position for 12 months or greater, estimated fair value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss		0
Marketable securities, in loss position, estimated fair value		21,465,000
Marketable securities, in loss position, gross unrealized losses		3,000
Foreign Agency Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	453,076,000	364,568,000
Available-for-sale securities, gross unrealized gains	49,000	127,000
Available-for-sale Securities, Gross Unrealized Loss	560,000	649,000
Marketable securities	452,565,000	364,046,000
Marketable securities, continuous unrealized loss position:
Marketable securities, in loss position for less than 12 months, estimated fair value	384,229,000	212,655,000
Marketable securities, in loss position for less than 12 months, gross unrealized losses	560,000	649,000
Marketable securities, in loss position for 12 months or greater, estimated fair value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	0	0
Marketable securities, in loss position, estimated fair value	384,229,000	212,655,000
Marketable securities, in loss position, gross unrealized losses	560,000	649,000
Foreign Government Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		25,125,000
Available-for-sale securities, gross unrealized gains		0
Available-for-sale Securities, Gross Unrealized Loss		10,000
Marketable securities	0	25,115,000
Marketable securities, continuous unrealized loss position:
Marketable securities, in loss position for less than 12 months, estimated fair value		25,161,000
Marketable securities, in loss position for less than 12 months, gross unrealized losses		10,000
Marketable securities, in loss position for 12 months or greater, estimated fair value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss		0
Marketable securities, in loss position, estimated fair value		25,161,000
Marketable securities, in loss position, gross unrealized losses		10,000
Bank Time Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	30,000,000
Available-for-sale securities, gross unrealized gains	0
Available-for-sale Securities, Gross Unrealized Loss	0
Marketable securities	$ 30,000,000	$ 0