Pro Forma Information (unaudited) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended				3 Months Ended								12 Months Ended			10 Months Ended	1 Months Ended		5 Months Ended	6 Months Ended	0 Months Ended	1 Months Ended
	Feb. 28, 2015	Apr. 30, 2014	Jan. 31, 2013	Jul. 31, 2012	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2014 property	Dec. 31, 2013 property	Jan. 31, 2015 property	Dec. 31, 2013 property	Sep. 30, 2014 property building	May 30, 2014	May 31, 2014
Pro Forma Information
Proceeds from sale of properties													$ 27,325	$ 92,550	$ 1,041
Gain (Loss) on Sale of Properties													5,453	37,392	(101)
Interest rate (as a percent)																5.875%
Mortgage debt assumed													15,630	12,266	121,793
Weighted average interest rate on debt (as a percent)					6.28%				6.25%				6.28%	6.25%			6.25%		6.25%
Common shares issued in public offering	31,050,000	15,525,000	11,500,000	13,800,000
Net proceeds from issuance of common shares issued in public offering	660,014	322,807	261,813	287,052									322,807	261,813	287,052
Principal amount of debt					1,750,000				1,100,000				1,750,000	1,100,000			1,100,000		1,100,000
Net proceeds after underwriting discounts from sale of senior unsecured notes		644,889
Pro forma results of operations
Total revenues													925,091	827,801
Net income													173,622	137,369
Per common share data:
Net income per share(in dollars per share)													$ 0.85	$ 0.68
Revenues					229,809	216,873	206,708	191,497	200,336	187,265	186,928	186,909	844,887	761,438	634,800
Interest Expense													135,114	117,819	117,240
MOBs
Pro Forma Information
Aggregate purchase price properties, excluding closing costs													1,204,393	202,824
Skilled nursing facilities
Pro Forma Information
Number of properties to be sold																3
Assisted living facility member
Pro Forma Information
Number of properties to be sold																3
Acquisition
Per common share data:
Revenues													68,181	12,306
Property operating expenses													14,826	4,057
Interest Expense													631	368
Acquisition | Senior living communities
Pro Forma Information
Number of properties acquired or agreed to be acquired													2	6
Acquisition | MOBs
Pro Forma Information
Number of properties acquired or agreed to be acquired													2	6
Number of properties acquired newly constructed																	1
Number of buildings acquired													3	7
Mortgage debt assumed													15,630
Acquisition | MOBs | Subsequent event
Pro Forma Information
Number of properties acquired or agreed to be acquired													23					23
Mortgage debt assumed																		30,000
Sale
Pro Forma Information
Number of properties to be sold																6			3
Gain (Loss) on Sale of Properties																5,452			37,392
Sale | Senior living communities
Pro Forma Information
Number of properties to be sold													6
Sale | MOBs
Pro Forma Information
Number of properties to be sold													3							3
Gain (Loss) on Sale of Properties																				0
Number of Buildings Sold																				3
Sale | Skilled nursing facilities
Pro Forma Information
Number of properties to be sold																			1
Senior unsecured notes 3.25%
Pro Forma Information
Interest rate (as a percent)		3.25%			3.25%								3.25%
Principal amount of debt		400,000			400,000								400,000
Senior unsecured notes 4.75%
Pro Forma Information
Interest rate (as a percent)		4.75%			4.75%								4.75%
Principal amount of debt		250,000			250,000								250,000
Unsecured Debt
Pro Forma Information
Interest rate (as a percent)					1.60%								1.60%
Weighted average interest rate on debt (as a percent)					1.60%								1.60%
Principal amount of debt					$ 350,000								$ 350,000									$ 350,000
Interest rate, description																					LIBOR
Interest rate added to the base rate (as a percent)																					1.40%	1.40%
Unsecured Debt | London Interbank Offered Rate (LIBOR) [Member]
Pro Forma Information
Interest rate, description																						LIBOR