Condensed consolidating financial statements - Condensed Consolidating Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Balance Sheet Statements Captions [Line Items]
Cash and cash equivalents	$ 448,215	$ 508,234
Restricted cash and equivalents	91,940	10,686
Accounts receivable, net	1,847,086	1,714,750
Other current assets	594,474	749,046
Current assets held for sale	5,947,786	5,761,642
Total current assets	8,929,501	8,744,358
Property and equipment, net	3,275,636	3,149,213
Intangible assets, net	97,609	113,827
Investments in subsidiaries	0	0
Intercompany receivables	0	0
Other long-term assets and investments	352,384	330,516
Goodwill	6,702,659	6,610,279	$ 6,015,375
Total assets	19,357,789	18,948,193
Current liabilities	3,435,483	1,856,107
Current liabilities held for sale	1,419,621	1,185,070
Intercompany payables	0	0
Long-term debt and other long-term liabilities	9,409,011	10,009,590
Noncontrolling interests subject to put provisions	1,064,412	1,011,360
Total DaVita Inc. shareholders' equity	3,824,649	4,690,029
Noncontrolling interests not subject to put provisions	204,613	196,037
Total equity	4,029,262	4,886,066
Total liabilities and equity	19,357,789	18,948,193
Consolidating adjustments
Condensed Balance Sheet Statements Captions [Line Items]
Cash and cash equivalents	0	0
Restricted cash and equivalents	0	0
Accounts receivable, net	0	0
Other current assets	0	0
Current assets held for sale	0	0
Total current assets	0	0
Property and equipment, net	0	0
Intangible assets, net	0	0
Investments in subsidiaries	(13,235,430)	(13,095,596)
Intercompany receivables	(4,974,797)	(4,991,160)
Other long-term assets and investments	0	0
Goodwill	0	0
Total assets	(18,210,227)	(18,086,756)
Current liabilities	0	0
Current liabilities held for sale	0	0
Intercompany payables	(4,974,797)	(4,991,160)
Long-term debt and other long-term liabilities	0	0
Noncontrolling interests subject to put provisions	467,314	436,758
Total DaVita Inc. shareholders' equity	(13,235,430)	(13,095,596)
Noncontrolling interests not subject to put provisions	(467,314)	(436,758)
Total equity	(13,702,744)	(13,532,354)
Total liabilities and equity	(18,210,227)	(18,086,756)
DaVita Inc. | Reportable Legal Entities
Condensed Balance Sheet Statements Captions [Line Items]
Cash and cash equivalents	296,697	149,305
Restricted cash and equivalents	1,004	1,002
Accounts receivable, net	0	0
Other current assets	37,185	67,025
Current assets held for sale	0	0
Total current assets	334,886	217,332
Property and equipment, net	466,162	408,010
Intangible assets, net	176	250
Investments in subsidiaries	10,071,347	10,009,874
Intercompany receivables	3,496,240	3,677,947
Other long-term assets and investments	54,853	47,297
Goodwill	0	0
Total assets	14,423,664	14,360,710
Current liabilities	1,815,234	238,706
Current liabilities held for sale	0	0
Intercompany payables	0	0
Long-term debt and other long-term liabilities	8,186,683	8,857,373
Noncontrolling interests subject to put provisions	597,098	574,602
Total DaVita Inc. shareholders' equity	3,824,649	4,690,029
Noncontrolling interests not subject to put provisions	0	0
Total equity	3,824,649	4,690,029
Total liabilities and equity	14,423,664	14,360,710
Guarantor subsidiaries | Reportable Legal Entities
Condensed Balance Sheet Statements Captions [Line Items]
Cash and cash equivalents	0	0
Restricted cash and equivalents	11,985	9,384
Accounts receivable, net	1,241,147	1,208,715
Other current assets	467,669	595,066
Current assets held for sale	4,999,748	4,992,067
Total current assets	6,720,549	6,805,232
Property and equipment, net	1,563,552	1,560,390
Intangible assets, net	43,704	50,971
Investments in subsidiaries	3,164,083	3,085,722
Intercompany receivables	0	0
Other long-term assets and investments	86,821	68,344
Goodwill	4,778,542	4,732,320
Total assets	16,357,251	16,302,979
Current liabilities	1,149,518	1,181,139
Current liabilities held for sale	892,548	739,294
Intercompany payables	3,485,322	3,690,042
Long-term debt and other long-term liabilities	758,516	682,630
Noncontrolling interests subject to put provisions	0	0
Total DaVita Inc. shareholders' equity	10,071,347	10,009,874
Noncontrolling interests not subject to put provisions	0	0
Total equity	10,071,347	10,009,874
Total liabilities and equity	16,357,251	16,302,979
Non- Guarantor subsidiaries | Reportable Legal Entities
Condensed Balance Sheet Statements Captions [Line Items]
Cash and cash equivalents	151,518	358,929
Restricted cash and equivalents	78,951	300
Accounts receivable, net	605,939	506,035
Other current assets	89,620	86,955
Current assets held for sale	948,038	769,575
Total current assets	1,874,066	1,721,794
Property and equipment, net	1,245,922	1,180,813
Intangible assets, net	53,729	62,606
Investments in subsidiaries	0	0
Intercompany receivables	1,478,557	1,313,213
Other long-term assets and investments	210,710	214,875
Goodwill	1,924,117	1,877,959
Total assets	6,787,101	6,371,260
Current liabilities	470,731	436,262
Current liabilities held for sale	527,073	445,776
Intercompany payables	1,489,475	1,301,118
Long-term debt and other long-term liabilities	463,812	469,587
Noncontrolling interests subject to put provisions	0	0
Total DaVita Inc. shareholders' equity	3,164,083	3,085,722
Noncontrolling interests not subject to put provisions	671,927	632,795
Total equity	3,836,010	3,718,517
Total liabilities and equity	$ 6,787,101	$ 6,371,260