Summary of Significant Accounting Policies (Details 7) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of intangible assets
Gross Carrying Amount	$ 130,233,000	$ 130,233,000
Accumulated Amortization	(95,298,000)	(85,644,000)
Net Carrying Amount	34,935,000	44,589,000
Amortization expense	9,700,000	10,700,000	10,800,000
Estimated amortization expense in future
2013	9,100,000
2014	9,100,000
2015	8,000,000
2016	5,300,000
2017	1,900,000
Customer agreements and lists
Summary of intangible assets
Gross Carrying Amount	121,490,000	121,490,000
Accumulated Amortization	(90,548,000)	(81,388,000)
Net Carrying Amount	30,942,000	40,102,000
Customer agreements and lists | Minimum
Summary of intangible assets
Estimated Useful Life	3 years	3 years
Customer agreements and lists | Maximum
Summary of intangible assets
Estimated Useful Life	18 years	18 years
Provider networks and other
Summary of intangible assets
Gross Carrying Amount	8,743,000	8,743,000
Accumulated Amortization	(4,750,000)	(4,256,000)
Net Carrying Amount	$ 3,993,000	$ 4,487,000
Provider networks and other | Minimum
Summary of intangible assets
Estimated Useful Life	5 years	5 years
Provider networks and other | Maximum
Summary of intangible assets
Estimated Useful Life	16 years	16 years