CONDENSED CONSOLIDATING INFORMATION (Unaudited) - Statement of Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenues:
Rental income	$ 384,028	$ 401,876	$ 1,129,099	$ 1,196,596
Income from loans and investments	18,108	32,985	105,706	85,499
Equity earnings in affiliates	0	0	0	0
Interest and other income	12,554	171	24,535	854
Total revenues	936,538	899,928	2,822,547	2,678,861
Expenses
Interest	107,581	113,869	331,973	336,245
Depreciation and amortization	218,579	213,407	675,363	655,298
Property-level operating expenses	428,389	376,207	1,262,715	1,111,024
Office building services costs	431	418	1,080	1,708
General, administrative and professional fees	39,677	33,317	113,507	100,560
Loss on extinguishment of debt, net	39,527	511	50,411	856
Merger-related expenses and deal costs	4,458	804	26,288	8,903
Other	1,244	13,030	7,891	16,066
Total expenses	839,886	751,563	2,469,228	2,230,660
Income before unconsolidated entities, income taxes, discontinued operations, real estate dispositions and noncontrolling interests	96,652	148,365	353,319	448,201
(Loss) income from unconsolidated entities	(716)	750	(47,826)	3,794
Income tax benefit	7,327	7,815	11,303	13,119
Income from continuing operations	103,263	156,930	316,796	465,114
Discontinued operations	0	(19)	(10)	(95)
Gain on real estate dispositions	(18)	(458,280)	(35,893)	(502,288)
Net income	103,281	615,191	352,679	967,307	$ 1,361,112
Net income attributable to noncontrolling interests	1,309	1,233	5,485	3,391
Net income attributable to common stockholders	101,972	613,958	347,194	963,916
Consolidated Elimination
Revenues:
Rental income	0	0	0	0
Income from loans and investments	0	0	0	0
Equity earnings in affiliates	(73,174)	(599,008)	(276,025)	(913,158)
Interest and other income	0	0	0	0
Total revenues	(73,174)	(599,008)	(276,025)	(913,158)
Expenses
Interest	0	0	0	0
Depreciation and amortization	0	0	0	0
Property-level operating expenses	0	0	0	0
Office building services costs	0	0	0	0
General, administrative and professional fees	0	0	0	0
Loss on extinguishment of debt, net	0	0	0	0
Merger-related expenses and deal costs	0	0	0	0
Other	0	0	0	0
Total expenses	0	0	0	0
Income before unconsolidated entities, income taxes, discontinued operations, real estate dispositions and noncontrolling interests	(73,174)	(599,008)	(276,025)	(913,158)
(Loss) income from unconsolidated entities	0	0	0	0
Income tax benefit	0	0	0	0
Income from continuing operations	(73,174)	(599,008)	(276,025)	(913,158)
Discontinued operations		0	0	0
Gain on real estate dispositions	0	0	0	0
Net income	(73,174)	(599,008)	(276,025)	(913,158)
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to common stockholders	(73,174)	(599,008)	(276,025)	(913,158)
Ventas, Inc.
Revenues:
Rental income	275	601	1,132	1,782
Income from loans and investments	387	309	1,150	908
Equity earnings in affiliates	74,048	594,857	278,103	909,605
Interest and other income	12,335	3	23,726	374
Total revenues	87,045	595,770	304,111	912,669
Expenses
Interest	(19,307)	(16,836)	(76,297)	(61,204)
Depreciation and amortization	1,365	1,314	4,081	4,140
Property-level operating expenses	0	0	0	0
Office building services costs	0	0	0	0
General, administrative and professional fees	2,744	100	2,892	412
Loss on extinguishment of debt, net	202	0	356	0
Merger-related expenses and deal costs	2,980	360	23,390	8,007
Other	28	1,626	4,524	1,743
Total expenses	(11,988)	(13,436)	(41,054)	(46,902)
Income before unconsolidated entities, income taxes, discontinued operations, real estate dispositions and noncontrolling interests	99,033	609,206	345,165	959,571
(Loss) income from unconsolidated entities	0	0	0	0
Income tax benefit	2,944	4,771	2,606	4,440
Income from continuing operations	101,977	613,977	347,771	964,011
Discontinued operations		(19)	(10)	(95)
Gain on real estate dispositions	5	0	567	0
Net income	101,972	613,958	347,194	963,916
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to common stockholders	101,972	613,958	347,194	963,916
Ventas Realty
Revenues:
Rental income	35,189	45,447	103,874	141,717
Income from loans and investments	0	0	0	0
Equity earnings in affiliates	0	0	0	0
Interest and other income	8	0	8	0
Total revenues	35,197	45,447	103,882	141,717
Expenses
Interest	80,255	82,007	245,210	238,312
Depreciation and amortization	1,411	1,455	4,277	6,062
Property-level operating expenses	77	69	231	235
Office building services costs	0	0	0	0
General, administrative and professional fees	4,477	4,240	13,142	13,570
Loss on extinguishment of debt, net	36,219	504	48,815	942
Merger-related expenses and deal costs	0	0	0	0
Other	25	0	25	0
Total expenses	122,464	88,275	311,700	259,121
Income before unconsolidated entities, income taxes, discontinued operations, real estate dispositions and noncontrolling interests	(87,267)	(42,828)	(207,818)	(117,404)
(Loss) income from unconsolidated entities	0	0	0	0
Income tax benefit	0	0	0	0
Income from continuing operations	(87,267)	(42,828)	(207,818)	(117,404)
Discontinued operations		0	0	0
Gain on real estate dispositions	0	(457,952)	0	(472,732)
Net income	(87,267)	415,124	(207,818)	355,328
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to common stockholders	(87,267)	415,124	(207,818)	355,328
Ventas Subsidiaries
Revenues:
Rental income	348,564	355,828	1,024,093	1,053,097
Income from loans and investments	17,721	32,676	104,556	84,591
Equity earnings in affiliates	(874)	4,151	(2,078)	3,553
Interest and other income	211	168	801	480
Total revenues	887,470	857,719	2,690,579	2,537,633
Expenses
Interest	46,633	48,698	163,060	159,137
Depreciation and amortization	215,803	210,638	667,005	645,096
Property-level operating expenses	428,312	376,138	1,262,484	1,110,789
Office building services costs	431	418	1,080	1,708
General, administrative and professional fees	32,456	28,977	97,473	86,578
Loss on extinguishment of debt, net	3,106	7	1,240	(86)
Merger-related expenses and deal costs	1,478	444	2,898	896
Other	1,191	11,404	3,342	14,323
Total expenses	729,410	676,724	2,198,582	2,018,441
Income before unconsolidated entities, income taxes, discontinued operations, real estate dispositions and noncontrolling interests	158,060	180,995	491,997	519,192
(Loss) income from unconsolidated entities	(716)	750	(47,826)	3,794
Income tax benefit	4,383	3,044	8,697	8,679
Income from continuing operations	161,727	184,789	452,868	531,665
Discontinued operations		0	0	0
Gain on real estate dispositions	(23)	(328)	(36,460)	(29,556)
Net income	161,750	185,117	489,328	561,221
Net income attributable to noncontrolling interests	1,309	1,233	5,485	3,391
Net income attributable to common stockholders	160,441	183,884	483,843	557,830
Resident Fees and Services
Revenues:
Other revenues	518,560	461,700	1,552,302	1,386,131
Resident Fees and Services | Consolidated Elimination
Revenues:
Other revenues	0	0	0	0
Resident Fees and Services | Ventas, Inc.
Revenues:
Other revenues	0	0	0	0
Resident Fees and Services | Ventas Realty
Revenues:
Other revenues	0	0	0	0
Resident Fees and Services | Ventas Subsidiaries
Revenues:
Other revenues	518,560	461,700	1,552,302	1,386,131
Office Building and Other Services Revenue
Revenues:
Other revenues	3,288	3,196	10,905	9,781
Office Building and Other Services Revenue | Consolidated Elimination
Revenues:
Other revenues	0	0	0	0
Office Building and Other Services Revenue | Ventas, Inc.
Revenues:
Other revenues	0	0	0	0
Office Building and Other Services Revenue | Ventas Realty
Revenues:
Other revenues	0	0	0	0
Office Building and Other Services Revenue | Ventas Subsidiaries
Revenues:
Other revenues	$ 3,288	$ 3,196	$ 10,905	$ 9,781