Investments and Fair Value Measurements-AFS FV and Unrealized Losses (Details 5) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Available-for-sale securities that were in an unrealized gain position
Less than 12 months, Fair Value	$ 277,810
Less than 12 months, Gross Unrealized Loss	(423)
Greater than 12 months, Fair Value	5,000
Greater than 12 months, Gross Unrealized Loss	(1)
U.S. Treasury and government agency securities [Member]
Available-for-sale securities that were in an unrealized gain position
Less than 12 months, Fair Value	4,199
Less than 12 months, Gross Unrealized Loss	0
Greater than 12 months, Fair Value	0
Greater than 12 months, Gross Unrealized Loss	0
U.S. Government-sponsored agency securities [Member]
Available-for-sale securities that were in an unrealized gain position
Less than 12 months, Fair Value	6,156
Less than 12 months, Gross Unrealized Loss	(1)
Greater than 12 months, Fair Value	0
Greater than 12 months, Gross Unrealized Loss	0
International Government Securities [Member]
Available-for-sale securities that were in an unrealized gain position
Less than 12 months, Fair Value	9,868
Less than 12 months, Gross Unrealized Loss	(15)
Greater than 12 months, Fair Value	0
Greater than 12 months, Gross Unrealized Loss	0
Corporate notes and bonds [Member]
Available-for-sale securities that were in an unrealized gain position
Less than 12 months, Fair Value	77,132
Less than 12 months, Gross Unrealized Loss	(68)
Greater than 12 months, Fair Value	5,000
Greater than 12 months, Gross Unrealized Loss	(1)
Asset-backed securities [Member]
Available-for-sale securities that were in an unrealized gain position
Less than 12 months, Fair Value	45,241
Less than 12 months, Gross Unrealized Loss	(43)
Greater than 12 months, Fair Value	0
Greater than 12 months, Gross Unrealized Loss	0
Mortgage Backed Securities, Other [Member]
Available-for-sale securities that were in an unrealized gain position
Less than 12 months, Fair Value	1,681
Less than 12 months, Gross Unrealized Loss	(22)
Greater than 12 months, Fair Value	0
Greater than 12 months, Gross Unrealized Loss	0
Municipal notes and bonds [Member]
Available-for-sale securities that were in an unrealized gain position
Less than 12 months, Fair Value	133,533
Less than 12 months, Gross Unrealized Loss	(274)
Greater than 12 months, Fair Value	0
Greater than 12 months, Gross Unrealized Loss	$ 0