Real Estate Properties (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended					6 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2013 item	Jun. 30, 2012 item	Jun. 30, 2013 item	Jun. 30, 2012 item	Jun. 30, 2013 MOBs item	Jun. 30, 2013 Senior living communities item	Dec. 31, 2012 Senior living communities item	Jun. 30, 2013 Senior living communities Sale item	Jun. 30, 2013 Discontinued operations, properties sold or held for sale MOBs item	Jun. 30, 2012 Discontinued operations, properties sold or held for sale MOBs	Jun. 30, 2013 Discontinued operations, properties sold or held for sale MOBs item	Jun. 30, 2012 Discontinued operations, properties sold or held for sale MOBs
Real estate properties
Rental income	$ 112,297	$ 108,407	$ 224,150	$ 215,435					$ 2,574	$ 2,579	$ 5,095	$ 5,056
Property operating expenses	(74,484)	(39,818)	(148,163)	(78,304)					(862)	(916)	(1,773)	(1,587)
Depreciation and amortization	(38,296)	(34,624)	(75,999)	(67,397)					(199)	(606)	(799)	(1,210)
Income from discontinued operations	1,513	1,057	2,523	2,259					1,513	1,057	2,523	2,259
Number of properties that met the criteria for discontinued operations	18	1	18	1	7	11	1		7		7
Number of properties to be sold								1
Number of units						856	120	112
Sale price of properties under agreement to be sold, excluding transaction costs								$ 2,600