Investments - Schedule Of Amortized Costs And Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	$ 31,085	[1]	$ 34,202	[1]
Fair Value	31,015		34,214
Net unrealized gain (loss) in AOCI	(70)		12
Pre-Refunded And Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	15,048	[1]	15,047	[1]
Fair Value	14,816		14,877
Net unrealized gain (loss) in AOCI	(232)		(170)
Short-Term Bond Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	14,016	[1]	17,014
Fair Value	14,178		17,196
Net unrealized gain (loss) in AOCI	162		182
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	1,659	[1]	1,779	[1]
Fair Value	1,659		1,779
Net unrealized gain (loss) in AOCI	0		0
Other Investment [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	362	[1]	362	[1]
Fair Value	362		362
Net unrealized gain (loss) in AOCI	$ 0		$ 0

[1] The cost basis represents the actual amount paid or the basis assumed following a permanent impairment of that asset.