Significant Accounting Policies (Goodwill and Other Intangible Assets) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Jun. 30, 2014	Sep. 30, 2014
Goodwill [Line Items]
Goodwill Impairment				$ 0
Goodwill, beginning of the period	558,886,000
Asset impairment	1,884,000	0
Goodwill, end of the period	558,886,000
Finite-Lived Intangible Assets
Gross Carrying Amount	71,000,000		71,000,000
Accumulated Amortization	(59,900,000)		(59,200,000)
Net Balance	11,100,000		11,800,000
Future Amortization Expense, Current to Five Succeeding Fiscal Years
2015	2,800,000
2016	2,200,000
2017	2,200,000
2018	2,100,000
2019	900,000
Provider Networks [Member]
Finite-Lived Intangible Assets
Gross Carrying Amount	41,500,000		41,500,000
Accumulated Amortization	(37,200,000)		(36,900,000)
Net Balance	4,300,000		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
Accumulated Amortization	(22,700,000)		(22,300,000)
Net Balance	6,800,000		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]
Fair Value to Carrying Value Ratio				190.00%	224.00%
Goodwill allocated to sale of business			7,000,000
Goodwill, end of the period	558,900,000		558,900,000
Goodwill [Member]
Goodwill [Line Items]
Asset impairment	$ 0		$ 7,000,000