Basis of Presentation and Significant Accounting Policies (Summary of Operating Revenues by Payor Source) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Total operating revenues, net of contractual allowances and discounts, Amount	$ 598,163	$ 608,636	$ 1,212,647	$ 1,215,108
Sales Revenue, Net [Member] | Payor Concentration Risk [Member]
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Concentration risk, percentage	100.00%	100.00%	100.00%	100.00%
Medicare [Member]
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Total operating revenues, net of contractual allowances and discounts, Amount	$ 167,549	$ 156,649	$ 343,083	$ 331,373
Medicare [Member] | Sales Revenue, Net [Member] | Payor Concentration Risk [Member]
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Concentration risk, percentage	28.00%	25.70%	28.30%	27.30%
Medicaid [Member]
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Total operating revenues, net of contractual allowances and discounts, Amount	$ 113,283	$ 103,972	$ 216,351	$ 208,306
Medicaid [Member] | Sales Revenue, Net [Member] | Payor Concentration Risk [Member]
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Concentration risk, percentage	18.90%	17.10%	17.80%	17.10%
Managed Care and Commercial [Member]
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Total operating revenues, net of contractual allowances and discounts, Amount	$ 230,595	$ 259,984	$ 474,879	$ 495,752
Managed Care and Commercial [Member] | Sales Revenue, Net [Member] | Payor Concentration Risk [Member]
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Concentration risk, percentage	38.60%	42.70%	39.20%	40.80%
Self-Pay [Member]
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Total operating revenues, net of contractual allowances and discounts, Amount	$ 59,171	$ 57,181	$ 123,925	$ 120,095
Self-Pay [Member] | Sales Revenue, Net [Member] | Payor Concentration Risk [Member]
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Concentration risk, percentage	9.90%	9.40%	10.20%	9.90%
Non-Patient [Member]
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Total operating revenues, net of contractual allowances and discounts, Amount	$ 27,565	$ 30,850	$ 54,409	$ 59,582
Non-Patient [Member] | Sales Revenue, Net [Member] | Payor Concentration Risk [Member]
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Concentration risk, percentage	4.60%	5.10%	4.50%	4.90%