Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 item	Mar. 31, 2013	Dec. 31, 2013
Segment Reporting
Number of operating segments	4
Number of reportable segments	3
Revenues:
Rental income	$ 112,055	$ 111,852
Residents fees and services	79,442	75,056
Total revenues	191,497	186,908
Expenses:
Property operating expenses	77,802	73,679
Depreciation	38,355	37,703
General and administrative	8,290	8,648
Acquisition related costs	122	1,903
Impairment of assets		1,304
Total expenses	124,569	123,237
Operating income	66,928	63,671
Interest and other income	105	173
Interest expense	(28,900)	(29,564)
Income from continuing operations before income tax expense and equity in earnings of an investee	38,133	34,280
Income tax expense	(191)	(140)
Equity in (losses) / earnings of an investee	(97)	76
Income from continuing operations	37,845	34,216
Discontinued Operations:
Income from discontinued operations	1,300	1,019
Impairment of assets from discontinued operations	(721)
Income before gain on sale of properties	38,424	35,235
Gain on sale of properties	156
Net income	38,580	35,235
Total assets	4,778,668	4,811,269	4,764,666
Triple Net Senior Living Communities
Revenues:
Rental income	54,890	56,765
Total revenues	54,890	56,765
Expenses:
Depreciation	15,637	16,917
Total expenses	15,637	16,917
Operating income	39,253	39,848
Interest expense	(6,388)	(6,463)
Income from continuing operations before income tax expense and equity in earnings of an investee	32,865	33,385
Income from continuing operations	32,865	33,385
Discontinued Operations:
Income before gain on sale of properties	32,865
Gain on sale of properties	156
Net income	33,021	33,385
Total assets	1,843,510	1,937,795
Managed Senior Living Communities
Revenues:
Residents fees and services	79,442	75,056
Total revenues	79,442	75,056
Expenses:
Property operating expenses	60,788	57,904
Depreciation	8,155	6,849
Total expenses	68,943	64,753
Operating income	10,499	10,303
Interest expense	(2,988)	(3,068)
Income from continuing operations before income tax expense and equity in earnings of an investee	7,511	7,235
Income from continuing operations	7,511	7,235
Discontinued Operations:
Income before gain on sale of properties	7,511
Net income	7,511	7,235
Total assets	949,468	954,155
MOBs
Revenues:
Rental income	52,763	50,683
Total revenues	52,763	50,683
Expenses:
Property operating expenses	17,014	15,775
Depreciation	13,615	12,989
Total expenses	30,629	28,764
Operating income	22,134	21,919
Interest expense	(1,337)	(1,348)
Income from continuing operations before income tax expense and equity in earnings of an investee	20,797	20,571
Income from continuing operations	20,797	20,571
Discontinued Operations:
Income from discontinued operations	1,300	1,019
Impairment of assets from discontinued operations	(721)
Income before gain on sale of properties	21,376
Net income	21,376	21,590
Total assets	1,717,000	1,728,516
All Other Operations
Revenues:
Rental income	4,402	4,404
Total revenues	4,402	4,404
Expenses:
Depreciation	948	948
General and administrative	8,290	8,648
Acquisition related costs	122	1,903
Impairment of assets		1,304
Total expenses	9,360	12,803
Operating income	(4,958)	(8,399)
Interest and other income	105	173
Interest expense	(18,187)	(18,685)
Income from continuing operations before income tax expense and equity in earnings of an investee	(23,040)	(26,911)
Income tax expense	(191)	(140)
Equity in (losses) / earnings of an investee	(97)	76
Income from continuing operations	(23,328)	(26,975)
Discontinued Operations:
Income before gain on sale of properties	(23,328)
Net income	(23,328)	(26,975)
Total assets	$ 268,689	$ 190,803