CONDENSED CONSOLIDATING INFORMATION (Unaudited) - Statement of Income (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenues:
Rental income	$ 384,809	$ 395,222
Resident fees and services	514,753	464,188
Office building and other services revenue	3,328	3,406
Income from loans and investments	31,181	20,146
Equity earnings in affiliates	0	0
Interest and other income	9,634	481
Total revenues	943,705	883,443
Expenses
Interest	111,363	108,804
Depreciation and amortization	233,150	217,783
Property-level operating expenses	412,913	368,987
Office building services costs	115	738
General, administrative and professional fees	37,174	33,961
Loss on extinguishment of debt, net	10,977	309
Merger-related expenses and deal costs	17,336	2,056
Other	3,120	1,188
Total expenses	826,148	733,826
Income before unconsolidated entities, income taxes, discontinued operations, real estate dispositions and noncontrolling interests	117,557	149,617
Income (loss) from unconsolidated entities	(40,739)	3,150
Income tax benefit	3,242	3,145
Income from continuing operations	80,060	155,912
Discontinued operations	(10)	(53)
Gain on real estate dispositions	48	43,289
Net income	80,098	199,148	$ 1,361,112
Net income attributable to noncontrolling interests	1,395	1,021
Net income attributable to common stockholders	78,703	198,127
Consolidated Elimination
Revenues:
Rental income	0	0
Resident fees and services	0	0
Office building and other services revenue	0	0
Income from loans and investments	0	0
Equity earnings in affiliates	(55,662)	(136,681)
Interest and other income	0	0
Total revenues	(55,662)	(136,681)
Expenses
Interest	0	0
Depreciation and amortization	0	0
Property-level operating expenses	0	0
Office building services costs	0	0
General, administrative and professional fees	0	0
Loss on extinguishment of debt, net	0	0
Merger-related expenses and deal costs	0	0
Other	0	0
Total expenses	0	0
Income before unconsolidated entities, income taxes, discontinued operations, real estate dispositions and noncontrolling interests	(55,662)	(136,681)
Income (loss) from unconsolidated entities	0	0
Income tax benefit	0	0
Income from continuing operations	(55,662)	(136,681)
Discontinued operations	0	0
Gain on real estate dispositions	0	0
Net income	(55,662)	(136,681)
Net income attributable to noncontrolling interests	0	0
Net income attributable to common stockholders	(55,662)	(136,681)
Ventas, Inc.
Revenues:
Rental income	601	585
Resident fees and services	0	0
Office building and other services revenue	0	0
Income from loans and investments	491	281
Equity earnings in affiliates	56,662	136,989
Interest and other income	9,323	343
Total revenues	67,077	138,198
Expenses
Interest	(28,661)	(16,600)
Depreciation and amortization	1,344	1,409
Property-level operating expenses	0	0
Office building services costs	0	0
General, administrative and professional fees	556	130
Loss on extinguishment of debt, net	0	0
Merger-related expenses and deal costs	16,246	1,863
Other	2,169	(349)
Total expenses	(8,346)	(13,547)
Income before unconsolidated entities, income taxes, discontinued operations, real estate dispositions and noncontrolling interests	75,423	151,745
Income (loss) from unconsolidated entities	0	0
Income tax benefit	3,242	3,145
Income from continuing operations	78,665	154,890
Discontinued operations	(10)	(53)
Gain on real estate dispositions	48	43,290
Net income	78,703	198,127
Net income attributable to noncontrolling interests	0	0
Net income attributable to common stockholders	78,703	198,127
Ventas Realty
Revenues:
Rental income	34,386	47,819
Resident fees and services	0	0
Office building and other services revenue	0	0
Income from loans and investments	0	0
Equity earnings in affiliates	0	0
Interest and other income	0	0
Total revenues	34,386	47,819
Expenses
Interest	82,312	74,789
Depreciation and amortization	1,444	2,371
Property-level operating expenses	72	83
Office building services costs	0	0
General, administrative and professional fees	4,050	4,700
Loss on extinguishment of debt, net	10,977	19
Merger-related expenses and deal costs	0	0
Other	0	0
Total expenses	98,855	81,962
Income before unconsolidated entities, income taxes, discontinued operations, real estate dispositions and noncontrolling interests	(64,469)	(34,143)
Income (loss) from unconsolidated entities	(35,504)	3,321
Income tax benefit	0	0
Income from continuing operations	(99,973)	(30,822)
Discontinued operations	0	0
Gain on real estate dispositions	0	0
Net income	(99,973)	(30,822)
Net income attributable to noncontrolling interests	0	0
Net income attributable to common stockholders	(99,973)	(30,822)
Ventas Subsidiaries
Revenues:
Rental income	349,822	346,818
Resident fees and services	514,753	464,188
Office building and other services revenue	3,328	3,406
Income from loans and investments	30,690	19,865
Equity earnings in affiliates	(1,000)	(308)
Interest and other income	311	138
Total revenues	897,904	834,107
Expenses
Interest	57,712	50,615
Depreciation and amortization	230,362	214,003
Property-level operating expenses	412,841	368,904
Office building services costs	115	738
General, administrative and professional fees	32,568	29,131
Loss on extinguishment of debt, net	0	290
Merger-related expenses and deal costs	1,090	193
Other	951	1,537
Total expenses	735,639	665,411
Income before unconsolidated entities, income taxes, discontinued operations, real estate dispositions and noncontrolling interests	162,265	168,696
Income (loss) from unconsolidated entities	(5,235)	(171)
Income tax benefit	0	0
Income from continuing operations	157,030	168,525
Discontinued operations	0	0
Gain on real estate dispositions	0	(1)
Net income	157,030	168,524
Net income attributable to noncontrolling interests	1,395	1,021
Net income attributable to common stockholders	$ 155,635	$ 167,503