CONDENSED CONSOLIDATING INFORMATION (Unaudited) - Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Net real estate investments	$ 21,652,044	$ 22,092,452
Cash and cash equivalents	92,543	81,355
Escrow deposits and restricted cash	71,039	106,898
Investment in and advances to affiliates	0	0
Goodwill	1,035,248	1,034,644
Assets held for sale	62,534	65,413
Other assets	580,102	573,779
Total assets	23,493,510	23,954,541
Liabilities:
Senior notes payable and other debt	11,039,812	11,276,062
Intercompany loans	0	0
Accrued interest	77,764	93,958
Accounts payable and other liabilities	1,134,570	1,183,489
Liabilities related to assets held for sale	60,023	60,265
Deferred income taxes	244,742	250,092
Total liabilities	12,556,911	12,863,866
Redeemable OP Unitholder and noncontrolling interests	132,555	158,490
Total equity	10,804,044	10,932,185	$ 10,528,753
Total liabilities and equity	23,493,510	23,954,541
Consolidated Elimination
Assets
Net real estate investments	0	0
Cash and cash equivalents	0	0
Escrow deposits and restricted cash	0	0
Investment in and advances to affiliates	(17,693,377)	(17,702,146)
Goodwill	0	0
Assets held for sale	0	0
Other assets	0	0
Total assets	(17,693,377)	(17,702,146)
Liabilities:
Senior notes payable and other debt	0	0
Intercompany loans	0	0
Accrued interest	0	0
Accounts payable and other liabilities	0	0
Liabilities related to assets held for sale	0	0
Deferred income taxes	0	0
Total liabilities	0	0
Redeemable OP Unitholder and noncontrolling interests	0	0
Total equity	(17,693,377)	(17,702,146)
Total liabilities and equity	(17,693,377)	(17,702,146)
Ventas, Inc.
Assets
Net real estate investments	3,708	1,844
Cash and cash equivalents	11,672	9,828
Escrow deposits and restricted cash	9,739	39,816
Investment in and advances to affiliates	14,893,299	14,786,086
Goodwill	0	0
Assets held for sale	0	0
Other assets	61,262	55,936
Total assets	14,979,680	14,893,510
Liabilities:
Senior notes payable and other debt	0	0
Intercompany loans	7,389,404	7,835,266
Accrued interest	(6,886)	(6,410)
Accounts payable and other liabilities	366,117	381,512
Liabilities related to assets held for sale	0	0
Deferred income taxes	244,742	250,092
Total liabilities	7,993,377	8,460,460
Redeemable OP Unitholder and noncontrolling interests	0	0
Total equity	6,986,303	6,433,050
Total liabilities and equity	14,979,680	14,893,510
Ventas Realty
Assets
Net real estate investments	118,075	119,508
Cash and cash equivalents	0	0
Escrow deposits and restricted cash	128	128
Investment in and advances to affiliates	2,800,078	2,916,060
Goodwill	0	0
Assets held for sale	0	0
Other assets	6,560	9,458
Total assets	2,924,841	3,045,154
Liabilities:
Senior notes payable and other debt	8,596,937	8,895,641
Intercompany loans	(6,127,269)	(7,127,624)
Accrued interest	65,964	77,691
Accounts payable and other liabilities	41,026	24,635
Liabilities related to assets held for sale	0	0
Deferred income taxes	0	0
Total liabilities	2,576,658	1,870,343
Redeemable OP Unitholder and noncontrolling interests	0	0
Total equity	348,183	1,174,811
Total liabilities and equity	2,924,841	3,045,154
Ventas Subsidiaries
Assets
Net real estate investments	21,530,261	21,971,100
Cash and cash equivalents	80,871	71,527
Escrow deposits and restricted cash	61,172	66,954
Investment in and advances to affiliates	0	0
Goodwill	1,035,248	1,034,644
Assets held for sale	62,534	65,413
Other assets	512,280	508,385
Total assets	23,282,366	23,718,023
Liabilities:
Senior notes payable and other debt	2,442,875	2,380,421
Intercompany loans	(1,262,135)	(707,642)
Accrued interest	18,686	22,677
Accounts payable and other liabilities	727,427	777,342
Liabilities related to assets held for sale	60,023	60,265
Deferred income taxes	0	0
Total liabilities	1,986,876	2,533,063
Redeemable OP Unitholder and noncontrolling interests	132,555	158,490
Total equity	21,162,935	21,026,470
Total liabilities and equity	$ 23,282,366	$ 23,718,023