CONDENSED CONSOLIDATING INFORMATION (Unaudited) - Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Net real estate investments	$ 20,763,713	$ 22,092,452
Cash and cash equivalents	93,684	81,355
Escrow deposits and restricted cash	64,419	106,898
Investment in and advances to affiliates	0	0
Goodwill	1,034,274	1,034,644
Assets held for sale	15,567	65,413
Other assets	727,477	573,779
Total assets	22,699,134	23,954,541
Liabilities:
Senior notes payable and other debt	10,402,897	11,276,062
Intercompany loans	0	0
Accrued interest	93,112	93,958
Accounts payable and other liabilities	1,133,902	1,183,489
Liabilities related to assets held for sale	896	60,265
Deferred income taxes	240,941	250,092
Total liabilities	11,871,748	12,863,866
Redeemable OP Unitholder and noncontrolling interests	149,817	158,490
Total equity	10,677,569	10,932,185	$ 10,528,753
Total liabilities and equity	22,699,134	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	(17,683,740)	(17,702,146)
Goodwill	0	0
Assets held for sale	0	0
Other assets	0	0
Total assets	(17,683,740)	(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	(17,683,740)	(17,702,146)
Total liabilities and equity	(17,683,740)	(17,702,146)
Ventas, Inc.
Assets
Net real estate investments	3,671	1,844
Cash and cash equivalents	10,292	7,129
Escrow deposits and restricted cash	7,573	39,816
Investment in and advances to affiliates	14,959,960	14,786,086
Goodwill	0	0
Assets held for sale	0	0
Other assets	52,886	55,936
Total assets	15,034,382	14,890,811
Liabilities:
Senior notes payable and other debt	0	0
Intercompany loans	7,358,514	7,835,685
Accrued interest	(8,262)	(6,410)
Accounts payable and other liabilities	356,239	377,536
Liabilities related to assets held for sale	0	0
Deferred income taxes	594	608
Total liabilities	7,707,085	8,207,419
Redeemable OP Unitholder and noncontrolling interests	12,242	12,237
Total equity	7,315,055	6,671,155
Total liabilities and equity	15,034,382	14,890,811
Ventas Realty
Assets
Net real estate investments	116,666	119,508
Cash and cash equivalents	0	0
Escrow deposits and restricted cash	128	128
Investment in and advances to affiliates	2,723,780	2,916,060
Goodwill	0	0
Assets held for sale	0	0
Other assets	10,030	9,458
Total assets	2,850,604	3,045,154
Liabilities:
Senior notes payable and other debt	8,041,058	8,895,641
Intercompany loans	(5,198,356)	(7,127,547)
Accrued interest	77,506	77,691
Accounts payable and other liabilities	31,034	24,635
Liabilities related to assets held for sale	0	0
Deferred income taxes	0	0
Total liabilities	2,951,242	1,870,420
Redeemable OP Unitholder and noncontrolling interests	0	0
Total equity	(100,638)	1,174,734
Total liabilities and equity	2,850,604	3,045,154
Ventas Subsidiaries
Assets
Net real estate investments	20,643,376	21,971,100
Cash and cash equivalents	83,392	74,226
Escrow deposits and restricted cash	56,718	66,954
Investment in and advances to affiliates	0	0
Goodwill	1,034,274	1,034,644
Assets held for sale	15,567	65,413
Other assets	664,561	508,385
Total assets	22,497,888	23,720,722
Liabilities:
Senior notes payable and other debt	2,361,839	2,380,421
Intercompany loans	(2,160,158)	(708,138)
Accrued interest	23,868	22,677
Accounts payable and other liabilities	746,629	781,318
Liabilities related to assets held for sale	896	60,265
Deferred income taxes	240,347	249,484
Total liabilities	1,213,421	2,786,027
Redeemable OP Unitholder and noncontrolling interests	137,575	146,253
Total equity	21,146,892	20,788,442
Total liabilities and equity	$ 22,497,888	$ 23,720,722