Financial Instruments Available-for-sale Securities (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 15,044	$ 239,113
GrossUnrealizedGain	6,022	434
GrossUnrealizedLoss	0	(159)
Fair Value	(21,066)	(239,388)
Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax	3,858	176
Available-for-sale Securities, Income Tax Expense on Change in Unrealized Holding Gain (Loss)	2,164	99
Proceeds from Sale of Available-for-sale Securities	342,045
Gross Realized Gains	1,311
Gross Realized Losses	(99)
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Cost		108,300
GrossUnrealizedGain		340
GrossUnrealizedLoss		(69)
Fair Value		(108,571)
U.S. government debt
Schedule of Available-for-sale Securities [Line Items]
Cost		106,335
GrossUnrealizedGain		60
GrossUnrealizedLoss		(79)
Fair Value		(106,316)
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost		24,478
GrossUnrealizedGain		34
GrossUnrealizedLoss		(11)
Fair Value		(24,501)
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	15,044
GrossUnrealizedGain	6,022
GrossUnrealizedLoss	0
Fair Value	$ (21,066)