Acquisitions of Real Estate Property (Estimated Fair Value) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
2015 Acquisitions
Business Acquisition [Line Items]
Land and improvements	$ 434,586
Buildings and improvements	3,642,295
Acquired lease intangibles	437,769
Other assets	849,166
Total assets acquired	5,363,816
Notes payable and other debt	177,857
Other liabilities	135,953
Total liabilities assumed	313,810
Net assets acquired	4,961,921
Noncontrolling interest assumed	88,085
Cash acquired	59,584
Equity issued	2,216,355
Total cash used	2,685,982
2015 Acquisitions | Triple-net leased properties
Business Acquisition [Line Items]
Land and improvements	190,566
Buildings and improvements	1,724,812
Acquired lease intangibles	169,362
Other assets	173,232
Total assets acquired	2,257,972
Notes payable and other debt	0
Other liabilities	43,811
Total liabilities assumed	43,811
Net assets acquired	2,214,161
2015 Acquisitions | Senior living operations
Business Acquisition [Line Items]
Land and improvements	70,713
Buildings and improvements	703,080
Acquired lease intangibles	83,867
Other assets	272,888
Total assets acquired	1,130,548
Notes payable and other debt	77,940
Other liabilities	45,408
Total liabilities assumed	123,348
Net assets acquired	1,007,200
2015 Acquisitions | MOB operations
Business Acquisition [Line Items]
Land and improvements	173,307
Buildings and improvements	1,214,403
Acquired lease intangibles	184,540
Other assets	403,046
Total assets acquired	1,975,296
Notes payable and other debt	99,917
Other liabilities	46,734
Total liabilities assumed	146,651
Net assets acquired	1,828,645
2014 Acquisitions
Business Acquisition [Line Items]
Land and improvements	145,867
Buildings and improvements	1,628,479
Acquired lease intangibles	65,335
Other assets	12,621
Total assets acquired	1,852,302
Notes payable and other debt	241,077
Other liabilities	133,077
Total liabilities assumed	374,154
Net assets acquired	1,478,148
Cash acquired	8,931
Total cash used	1,469,217
2014 Acquisitions | Triple-net leased properties
Business Acquisition [Line Items]
Land and improvements	45,586
Buildings and improvements	546,849
Acquired lease intangibles	28,883
Other assets	227
Total assets acquired	621,545
Notes payable and other debt	12,927
Other liabilities	8,609
Total liabilities assumed	21,536
Net assets acquired	600,009
Cash acquired	227
Total cash used	599,782
2014 Acquisitions | Senior living operations
Business Acquisition [Line Items]
Land and improvements	100,281
Buildings and improvements	1,081,630
Acquired lease intangibles	36,452
Other assets	12,394
Total assets acquired	1,230,757
Notes payable and other debt	228,150
Other liabilities	124,468
Total liabilities assumed	352,618
Net assets acquired	878,139
Cash acquired	8,704
Total cash used	869,435
2013 Acquisitions
Business Acquisition [Line Items]
Land and improvements	100,908
Buildings and improvements	1,521,596
Acquired lease intangibles	36,227
Other assets	8,345
Total assets acquired	1,667,076
Notes payable and other debt	41,436
Other liabilities	30,218
Total liabilities assumed	71,654
Net assets acquired	1,583,637
Noncontrolling interest assumed	11,785
Cash acquired	2,150
Total cash used	1,581,487
2013 Acquisitions | Triple-net leased properties
Business Acquisition [Line Items]
Land and improvements	51,419
Buildings and improvements	803,227
Acquired lease intangibles	8,945
Other assets	3,285
Total assets acquired	866,876
Notes payable and other debt	36,300
Other liabilities	11,423
Total liabilities assumed	47,723
Net assets acquired	809,040
Noncontrolling interest assumed	10,113
Cash acquired	753
Total cash used	808,287
2013 Acquisitions | Senior living operations
Business Acquisition [Line Items]
Land and improvements	45,566
Buildings and improvements	579,577
Acquired lease intangibles	16,920
Other assets	2,607
Total assets acquired	644,670
Notes payable and other debt	5,136
Other liabilities	12,285
Total liabilities assumed	17,421
Net assets acquired	627,249
Noncontrolling interest assumed	0
Cash acquired	0
Total cash used	627,249
2013 Acquisitions | MOB operations
Business Acquisition [Line Items]
Land and improvements	3,923
Buildings and improvements	138,792
Acquired lease intangibles	10,362
Other assets	2,453
Total assets acquired	155,530
Notes payable and other debt	0
Other liabilities	6,510
Total liabilities assumed	6,510
Net assets acquired	147,348
Noncontrolling interest assumed	1,672
Cash acquired	1,397
Total cash used	$ 145,951