Significant Accounting Policies (Goodwill and Other Intangible Assets) (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Goodwill [Line Items]
Goodwill Impairment	$ 0		$ 0
Goodwill, beginning of the period			558,886,000
Asset impairment	0	$ 0	1,884,000	$ 0	$ 87,200,000
Goodwill, end of the period	558,886,000		558,886,000		558,886,000
Finite-Lived Intangible Assets
Gross Carrying Amount	71,000,000		71,000,000		71,000,000
Accumulated Amortization	(60,600,000)		(60,600,000)		(59,200,000)
Net Balance	10,400,000		10,400,000		11,800,000
Future Amortization Expense, Current to Five Succeeding Fiscal Years
2015	2,800,000		2,800,000
2016	2,200,000		2,200,000
2017	2,200,000		2,200,000
2018	2,100,000		2,100,000
2019	900,000		900,000
Provider Networks [Member]
Finite-Lived Intangible Assets
Gross Carrying Amount	41,500,000		41,500,000		41,500,000
Accumulated Amortization	(37,500,000)		(37,500,000)		(36,900,000)
Net Balance	4,000,000		$ 4,000,000		$ 4,600,000
Weighted Average Life (in years)			18 years 10 months 24 days		18 years 10 months 24 days
Customer Relationships and Other [Member]
Finite-Lived Intangible Assets
Gross Carrying Amount	29,500,000		$ 29,500,000		$ 29,500,000
Accumulated Amortization	(23,100,000)		(23,100,000)		(22,300,000)
Net Balance	6,400,000		$ 6,400,000		$ 7,200,000
Weighted Average Life (in years)			11 years 1 month 6 days		11 years 1 month 6 days
Western Region Operations [Member]
Goodwill [Line Items]
Goodwill, beginning of the period			$ 558,900,000
Goodwill, end of the period	558,900,000		558,900,000		$ 558,900,000
Goodwill [Member]
Goodwill [Line Items]
Asset impairment	$ 0		$ 0		$ 7,000,000