Fair Value Measurements (Details 2) (Investments Valued Using Level 3 Inputs, USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Investments Valued Using Level 3 Inputs
Investments measured at fair value on a recurring basis using significant unobservable inputs (Level 3)
Balance at the beginning of the period	$ 34,350
Purchases		40
Total gains and losses included in gain on investments	(1,163)
Total gains and losses included in accumulated other comprehensive income	33,329	337
Cost basis of shares sold	(40)
Balance at the end of the period	$ 66,476	$ 377