Investments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Schedule of Available-for-sale Securities
Total, cost	$ 40,317		$ 41,605
Gross unrealized gains	8,681		7,536
Gross unrealized losses	(608)		(677)
Marketable equity securities, carrying value	39,404
Total available-for-sale investments, carrying value	48,390		48,464
Available-for-sale Securities, Continuous Unrealized Loss Position
Less than 12 months, fair value	3,977		5,961
Less than 12 months, gross unrealized loss	259		627
Greater than 12 months, fair value	3,678		2,249
Greater than 12 months, gross unrealized loss	349		50
Corporate Bonds
Schedule of Available-for-sale Securities
Fixed maturities, cost	8,748		7,758
Gross unrealized gains	286		324
Gross unrealized losses	(48)		(56)
Fixed maturities, carrying value	8,986		8,026
Available-for-sale Securities, Continuous Unrealized Loss Position
Less than 12 months, fair value	1,662		768
Less than 12 months, gross unrealized loss	10		12
Greater than 12 months, fair value	2,210		2,204
Greater than 12 months, gross unrealized loss	38		44
Marketable Equity Securities
Schedule of Available-for-sale Securities
Marketable equity securities, cost	31,569		33,847
Gross unrealized gains	8,395		7,212
Gross unrealized losses	(560)		(621)
Marketable equity securities, carrying value	39,404		40,438
Available-for-sale Securities, Continuous Unrealized Loss Position
Less than 12 months, fair value	2,315		5,193
Less than 12 months, gross unrealized loss	249		615
Greater than 12 months, fair value	1,468		45
Greater than 12 months, gross unrealized loss	311		6
Impairment losses, available-for-sale securities	$ 9	$ 841