Significant Accounting Policies (Health Plan Services Health Care Cost) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Health Care Organization Revenue and Expense [Line Items]
Health plan services	$ 2,268,736	$ 2,343,659
Incurred claims related to 2011 and prior [Member]
Health Care Organization Revenue and Expense [Line Items]
Health plan services		25,000
Incurred claims, Prior Period net [Member]
Health Care Organization Revenue and Expense [Line Items]
Health plan services	$ 0