Note 6. Cash, Cash Equivalents, and Marketable Securities (Details) - Available For Sale (USD $)	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Unrealized Gain (Loss)	$ (1,000,000)	$ 900,000
Available-for-sale securities, amortized cost	183,357,000	347,260,000
Available-for-sale securities, gross unrealized gains	84,000	1,164,000
Available-for-sale securities, gross unrealized losses	1,103,000	264,000
Available-for-sale Securities, estimated fair value	182,338,000	348,160,000
Marketable securities, continuous unrealized loss position:
Marketable securities, in loss position for less than 12 months, estimated fair value	115,035,000	95,388,000
Marketable securities, in loss position for less than 12 months, gross unrealized losses	1,103,000	264,000
Marketable securities, in loss position for 12 months or greater, estimated fair value	0	0
Marketable securities, in loss position for 12 months or greater, gross unrealized losses	0	0
Marketable securities, in loss position, estimated fair value	115,035,000	95,388,000
Marketable securities, in loss position, gross unrealized losses	1,103,000	264,000
Available For Sale Securities Debt Maturities Within One Year [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	66,146,000	167,499,000
Available-for-sale securities, gross unrealized gains	30,000	398,000
Available-for-sale securities, gross unrealized losses	30,000	8,000
Available-for-sale Securities, estimated fair value	66,146,000	167,889,000
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	97,538,000	177,268,000
Available-for-sale securities, gross unrealized gains	54,000	759,000
Available-for-sale securities, gross unrealized losses	854,000	256,000
Available-for-sale Securities, estimated fair value	96,738,000	177,771,000
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	19,673,000	2,493,000
Available-for-sale securities, gross unrealized gains	0	7,000
Available-for-sale securities, gross unrealized losses	219,000	0
Available-for-sale Securities, estimated fair value	19,454,000	2,500,000
Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	9,192,000	13,340,000
Available-for-sale securities, gross unrealized gains	1,000	3,000
Available-for-sale securities, gross unrealized losses	0	0
Available-for-sale Securities, estimated fair value	9,193,000	13,343,000
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	55,150,000	98,148,000
Available-for-sale securities, gross unrealized gains	13,000	592,000
Available-for-sale securities, gross unrealized losses	152,000	138,000
Available-for-sale Securities, estimated fair value	55,011,000	98,602,000
Marketable securities, continuous unrealized loss position:
Marketable securities, in loss position for less than 12 months, estimated fair value	47,763,000	33,018,000
Marketable securities, in loss position for less than 12 months, gross unrealized losses	152,000	138,000
Marketable securities, in loss position for 12 months or greater, estimated fair value	0	0
Marketable securities, in loss position for 12 months or greater, gross unrealized losses	0	0
Marketable securities, in loss position, estimated fair value	47,763,000	33,018,000
Marketable securities, in loss position, gross unrealized losses	152,000	138,000
Federal Agency Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	50,035,000	45,858,000
Available-for-sale securities, gross unrealized gains	54,000	21,000
Available-for-sale securities, gross unrealized losses	8,000	4,000
Available-for-sale Securities, estimated fair value	50,081,000	45,875,000
Marketable securities, continuous unrealized loss position:
Marketable securities, in loss position for less than 12 months, estimated fair value	6,744,000	11,721,000
Marketable securities, in loss position for less than 12 months, gross unrealized losses	8,000	4,000
Marketable securities, in loss position for 12 months or greater, estimated fair value	0	0
Marketable securities, in loss position for 12 months or greater, gross unrealized losses	0	0
Marketable securities, in loss position, estimated fair value	6,744,000	11,721,000
Marketable securities, in loss position, gross unrealized losses	8,000	4,000
Foreign Agency Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	11,473,000	132,860,000
Available-for-sale securities, gross unrealized gains	0	425,000
Available-for-sale securities, gross unrealized losses	545,000	120,000
Available-for-sale Securities, estimated fair value	10,928,000	133,165,000
Marketable securities, continuous unrealized loss position:
Marketable securities, in loss position for less than 12 months, estimated fair value	8,176,000	46,134,000
Marketable securities, in loss position for less than 12 months, gross unrealized losses	545,000	120,000
Marketable securities, in loss position for 12 months or greater, estimated fair value	0	0
Marketable securities, in loss position for 12 months or greater, gross unrealized losses	0	0
Marketable securities, in loss position, estimated fair value	8,176,000	46,134,000
Marketable securities, in loss position, gross unrealized losses	545,000	120,000
Foreign Government Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	9,128,000	9,137,000
Available-for-sale securities, gross unrealized gains	1,000	8,000
Available-for-sale securities, gross unrealized losses	9,000	2,000
Available-for-sale Securities, estimated fair value	9,120,000	9,143,000
Marketable securities, continuous unrealized loss position:
Marketable securities, in loss position for less than 12 months, estimated fair value	6,361,000	4,515,000
Marketable securities, in loss position for less than 12 months, gross unrealized losses	9,000	2,000
Marketable securities, in loss position for 12 months or greater, estimated fair value	0	0
Marketable securities, in loss position for 12 months or greater, gross unrealized losses	0	0
Marketable securities, in loss position, estimated fair value	6,361,000	4,515,000
Marketable securities, in loss position, gross unrealized losses	9,000	2,000
Supranational Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	46,380,000	47,917,000
Available-for-sale securities, gross unrealized gains	0	115,000
Available-for-sale securities, gross unrealized losses	389,000	0
Available-for-sale Securities, estimated fair value	45,991,000	48,032,000
Marketable securities, continuous unrealized loss position:
Marketable securities, in loss position for less than 12 months, estimated fair value	45,991,000
Marketable securities, in loss position for less than 12 months, gross unrealized losses	389,000
Marketable securities, in loss position for 12 months or greater, estimated fair value	0
Marketable securities, in loss position for 12 months or greater, gross unrealized losses	0
Marketable securities, in loss position, estimated fair value	45,991,000
Marketable securities, in loss position, gross unrealized losses	389,000
US Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	1,999,000
Available-for-sale securities, gross unrealized gains	15,000
Available-for-sale securities, gross unrealized losses	0
Available-for-sale Securities, estimated fair value	$ 2,014,000