Borrowing Arrangements (Senior Notes) (Details) $ in Millions	1 Months Ended							12 Months Ended
	Sep. 30, 2018 USD ($)	Aug. 31, 2018 USD ($)	Apr. 30, 2018 USD ($)	Feb. 28, 2018 USD ($)	Jun. 30, 2017 CAD ($)	Apr. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 03, 2019 USD ($)	Dec. 31, 2018 CAD ($)
Debt Instrument [Line Items]
Long-term debt, gross								$ 10,829,702,000	$ 11,365,633,000
Proceeds from issuance of debt								2,549,473,000	1,111,649,000	$ 893,218,000
Loss on extinguishment of debt, net								58,254,000	754,000	$ 2,779,000
3.10% Senior Notes due 2023
Debt Instrument [Line Items]
Long-term debt, gross							$ 400,000,000.0	$ 400,000,000	400,000,000
Interest rate							3.10%	3.10%				3.10%
Public offering price as percent of par							99.28%
Proceeds from issuance of debt							$ 397,100,000
Senior Notes Due 2027
Debt Instrument [Line Items]
Long-term debt, gross							$ 400,000,000.0
Interest rate							3.85%
Public offering price as percent of par							99.20%
Proceeds from public offering sale of debt							$ 396,800,000
1.250% Senior Notes due 2017
Debt Instrument [Line Items]
Interest rate						1.25%
Repayments of debt						$ 300,000,000.0
2.55% Senior Notes 2023
Debt Instrument [Line Items]
Long-term debt, gross					$ 275.0
Interest rate					2.55%
Public offering price as percent of par					99.95%
4.00% Senior Notes due 2019
Debt Instrument [Line Items]
Interest rate			4.00%	4.00%
Public offering price as percent of par				101.83%
Debt instrument, repurchase amount				$ 502,100,000
Loss on extinguishment of debt, net			$ 1,800,000	$ (11,000,000.0)
Repayments of long-term debt			$ 97,900,000
2.00% Senior Notes, Due 2018
Debt Instrument [Line Items]
Long-term debt, gross								$ 0	700,000,000
Interest rate				2.00%				2.00%				2.00%
Repayments of debt				$ 700,000,000.0
4.00% Senior Notes due 2028
Debt Instrument [Line Items]
Long-term debt, gross				$ 650,000,000.0				$ 650,000,000	0
Interest rate				4.00%				4.00%				4.00%
Public offering price as percent of par				99.23%
Proceeds from issuance of debt				$ 645,000,000.0
4.40% Senior Notes due 2029
Debt Instrument [Line Items]
Long-term debt, gross		$ 750,000,000.0						$ 750,000,000	0
Interest rate		4.40%						4.40%				4.40%
Public offering price as percent of par		99.95%
Proceeds from issuance of debt		$ 749,700,000
4.750% Senior Notes, due 2021
Debt Instrument [Line Items]
Interest rate	4.75%	4.75%
Public offering price as percent of par		104.56%
Loss on extinguishment of debt, net	$ 7,600,000	$ 28,300,000
Repayments of long-term debt	$ 150,500,000	$ 549,500,000
5.45% Senior Notes due 2043
Debt Instrument [Line Items]
Long-term debt, gross								$ 258,750,000	$ 258,750,000
Interest rate								5.45%				5.45%
Loss on extinguishment of debt, net								$ 7,100,000
6.90% Senior Notes Due 2037 | Senior Notes
Debt Instrument [Line Items]
Interest rate								6.90%				6.90%
6.59% Senior Notes Due 2038 | Senior Notes
Debt Instrument [Line Items]
Interest rate								6.59%				6.59%
Ventas Realty Limited Partnership | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross								$ 7,000,000,000.0
Ventas Capital Corporation and Ventas Realty | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross								1,900,000,000
Ventas Canada Finance Limited | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross												$ 1,200.0
Nationwide Health Properties Acquisitions | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross								$ 75,200,000
Subsequent Event | 5.45% Senior Notes due 2043
Debt Instrument [Line Items]
Interest rate											5.45%
Debt instrument, repurchase amount											$ 258,800,000
Canadian Dollars | 2.55% Senior Notes 2023
Debt Instrument [Line Items]
Proceeds from public offering sale of debt					$ 274.9
Canadian Dollars | Unsecured Term Loan Due 2019
Debt Instrument [Line Items]
Repayments of debt					$ 124.4