Significant Accounting Policies (Goodwill and Other Intangible Assets) (Details) (USD $)	12 Months Ended				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2012	Dec. 31, 2012 Provider Networks [Member]	Dec. 31, 2011 Provider Networks [Member]	Dec. 31, 2012 Customer Relationships [Member]	Dec. 31, 2011 Customer Relationships [Member]	Dec. 31, 2012 Western Region Operations [Member]	Jun. 30, 2012 Western Region Operations [Member]	Dec. 31, 2011 Western Region Operations [Member]	Jun. 30, 2011 Western Region Operations [Member]	Dec. 31, 2010 Western Region Operations [Member]
Significant Accounting Policies [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss				$ 0
Fair value to carrying value ratio										115.00%		180.00%
Goodwill	565,886,000	605,886,000	605,900,000						565,900,000		605,900,000		605,900,000
Goodwill allocated to business sold	40,000,000								(40,000,000)
Finite-Lived Intangible Assets
Gross Carrying Amount	70,000,000	70,000,000			40,500,000	40,500,000	29,500,000	29,500,000
Accumulated Amortization	(52,700,000)	(49,300,000)			(34,600,000)	(33,600,000)	(18,100,000)	(15,700,000)
Net Balance	17,300,000	20,700,000			5,900,000	6,900,000	11,400,000	13,800,000
Weighted Average Life (in years)					19 years 4 months 24 days	19 years 4 months 24 days	11 years 1 month 6 days	11 years 1 month 6 days
Amortization expense	3,400,000	3,500,000	3,800,000
Future Amortization Expense
Estimated annual pretax amortization expense, 2013	3,400,000
Estimated annual pretax amortization expense, 2014	2,800,000
Estimated annual pretax amortization expense, 2015	2,600,000
Estimated annual pretax amortization expense, 2016	2,000,000
Estimated annual pretax amortization expense, 2017	$ 2,000,000