Property Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012 property		Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of Company's investment
Number of owned real estate properties	202
Number of real estate investments	207
Land and Land Held for Development	$ 187,046	[1]
Buildings, Improvements, Lease Intangibles and CIP	2,625,538
Personal Property	19,100
Gross real estate asset, Total	2,841,297		2,841,453	2,614,557	2,250,879
Total real estate investments	2,995,141
Accumulated Depreciation	(586,725)
Mortgage Notes Receivable [Member]
Summary of Company's investment
Number of real estate investments	4
Land and Land Held for Development	0	[1]
Buildings, Improvements, Lease Intangibles and CIP	0
Personal Property	0
Gross real estate asset, Total	162,191
Accumulated Depreciation	0
Land Held for Development and Corporate Property [Member]
Summary of Company's investment
Number of owned real estate properties	0
Land and Land Held for Development	25,171	[1]
Buildings, Improvements, Lease Intangibles and CIP	0
Personal Property	15,037
Gross real estate asset, Total	40,208
Accumulated Depreciation	(9,084)
Land Held for Development [Member]
Summary of Company's investment
Number of owned real estate properties	0
Land and Land Held for Development	25,171	[1]
Buildings, Improvements, Lease Intangibles and CIP
Personal Property	0
Gross real estate asset, Total	25,171
Accumulated Depreciation	(64)
Corporate Property [Member]
Summary of Company's investment
Number of owned real estate properties	0
Land and Land Held for Development	0	[1]
Buildings, Improvements, Lease Intangibles and CIP	0
Personal Property	15,037
Gross real estate asset, Total	15,037
Accumulated Depreciation	(9,020)
Owned Property [Member]
Summary of Company's investment
Number of owned real estate properties	202
Land and Land Held for Development	187,046	[1]
Buildings, Improvements, Lease Intangibles and CIP	2,625,538
Personal Property	19,100
Gross real estate asset, Total	2,831,684
Accumulated Depreciation	(586,725)
Unconsolidated joint venture investment [Member]
Summary of Company's investment
Number of real estate investments	1
Land and Land Held for Development	0	[1]
Buildings, Improvements, Lease Intangibles and CIP	0
Personal Property	0
Gross real estate asset, Total	1,266
Accumulated Depreciation	0
Medical office/outpatient [Member]
Summary of Company's investment
Number of owned real estate properties	177
Land and Land Held for Development	139,292	[1]
Buildings, Improvements, Lease Intangibles and CIP	2,234,223
Personal Property	3,427
Gross real estate asset, Total	2,376,942
Accumulated Depreciation	(468,332)
Medical office/outpatient [Member] | California [Member]
Summary of Company's investment
Number of owned real estate properties	9
Land and Land Held for Development	17,430	[1]
Buildings, Improvements, Lease Intangibles and CIP	96,873
Personal Property	218
Gross real estate asset, Total	114,521
Accumulated Depreciation	(44,829)
Medical office/outpatient [Member] | Colorado [Member]
Summary of Company's investment
Number of owned real estate properties	7
Land and Land Held for Development	4,474	[1]
Buildings, Improvements, Lease Intangibles and CIP	130,473
Personal Property	270
Gross real estate asset, Total	135,217
Accumulated Depreciation	(7,946)
Medical office/outpatient [Member] | Indiana [Member]
Summary of Company's investment
Number of owned real estate properties	4
Land and Land Held for Development	3,891	[1]
Buildings, Improvements, Lease Intangibles and CIP	96,213
Personal Property	0
Gross real estate asset, Total	100,104
Accumulated Depreciation	(12,772)
Medical office/outpatient [Member] | Iowa [Member]
Summary of Company's investment
Number of owned real estate properties	8
Land and Land Held for Development	13,673	[1]
Buildings, Improvements, Lease Intangibles and CIP	86,018
Personal Property	104
Gross real estate asset, Total	99,795
Accumulated Depreciation	(8,216)
Medical office/outpatient [Member] | Florida [Member]
Summary of Company's investment
Number of owned real estate properties	9
Land and Land Held for Development	6,241	[1]
Buildings, Improvements, Lease Intangibles and CIP	91,426
Personal Property	269
Gross real estate asset, Total	97,936
Accumulated Depreciation	(42,171)
Medical office/outpatient [Member] | Hawaii [Member]
Summary of Company's investment
Number of owned real estate properties	3
Land and Land Held for Development	8,327	[1]
Buildings, Improvements, Lease Intangibles and CIP	110,014
Personal Property	56
Gross real estate asset, Total	118,397
Accumulated Depreciation	(11,093)
Medical office/outpatient [Member] | North Carolina [Member]
Summary of Company's investment
Number of owned real estate properties	15
Land and Land Held for Development	1,715	[1]
Buildings, Improvements, Lease Intangibles and CIP	149,503
Personal Property	101
Gross real estate asset, Total	151,319
Accumulated Depreciation	(26,102)
Medical office/outpatient [Member] | Tennessee [Member]
Summary of Company's investment
Number of owned real estate properties	16
Land and Land Held for Development	8,644	[1]
Buildings, Improvements, Lease Intangibles and CIP	166,412
Personal Property	191
Gross real estate asset, Total	175,247
Accumulated Depreciation	(48,710)
Medical office/outpatient [Member] | Texas [Member]
Summary of Company's investment
Number of owned real estate properties	45
Land and Land Held for Development	42,692	[1]
Buildings, Improvements, Lease Intangibles and CIP	602,926
Personal Property	1,384
Gross real estate asset, Total	647,002
Accumulated Depreciation	(122,216)
Medical office/outpatient [Member] | Virginia [Member]
Summary of Company's investment
Number of owned real estate properties	13
Land and Land Held for Development	2,451	[1]
Buildings, Improvements, Lease Intangibles and CIP	189,024
Personal Property	185
Gross real estate asset, Total	191,660
Accumulated Depreciation	(27,083)
Medical office/outpatient [Member] | Washington [Member]
Summary of Company's investment
Number of owned real estate properties	6
Land and Land Held for Development	5,110	[1]
Buildings, Improvements, Lease Intangibles and CIP	142,411
Personal Property	223
Gross real estate asset, Total	147,744
Accumulated Depreciation	(11,577)
Medical office/outpatient [Member] | Other (17 states) [Member]
Summary of Company's investment
Number of owned real estate properties	42
Land and Land Held for Development	24,644	[1]
Buildings, Improvements, Lease Intangibles and CIP	372,930
Personal Property	426
Gross real estate asset, Total	398,000
Accumulated Depreciation	(105,617)
Inpatient [Member]
Summary of Company's investment
Number of owned real estate properties	15
Land and Land Held for Development	20,682	[1]
Buildings, Improvements, Lease Intangibles and CIP	347,462
Personal Property	0
Gross real estate asset, Total	368,144
Accumulated Depreciation	(86,213)
Inpatient [Member] | California [Member]
Summary of Company's investment
Number of owned real estate properties	1
Land and Land Held for Development	0	[1]
Buildings, Improvements, Lease Intangibles and CIP	12,688
Personal Property	0
Gross real estate asset, Total	12,688
Accumulated Depreciation	(5,979)
Inpatient [Member] | Indiana [Member]
Summary of Company's investment
Number of owned real estate properties	1
Land and Land Held for Development	1,071	[1]
Buildings, Improvements, Lease Intangibles and CIP	42,335
Personal Property	0
Gross real estate asset, Total	43,406
Accumulated Depreciation	(7,056)
Inpatient [Member] | Florida [Member]
Summary of Company's investment
Number of owned real estate properties	1
Land and Land Held for Development	0	[1]
Buildings, Improvements, Lease Intangibles and CIP	11,703
Personal Property	0
Gross real estate asset, Total	11,703
Accumulated Depreciation	(4,273)
Inpatient [Member] | Texas [Member]
Summary of Company's investment
Number of owned real estate properties	4
Land and Land Held for Development	8,201	[1]
Buildings, Improvements, Lease Intangibles and CIP	137,990
Personal Property	0
Gross real estate asset, Total	146,191
Accumulated Depreciation	(13,985)
Inpatient [Member] | Alabama [Member]
Summary of Company's investment
Number of owned real estate properties	1
Land and Land Held for Development	0	[1]
Buildings, Improvements, Lease Intangibles and CIP	17,722
Personal Property	0
Gross real estate asset, Total	17,722
Accumulated Depreciation	(6,470)
Inpatient [Member] | Pennsylvania [Member]
Summary of Company's investment
Number of owned real estate properties	6
Land and Land Held for Development	7,769	[1]
Buildings, Improvements, Lease Intangibles and CIP	112,653
Personal Property	0
Gross real estate asset, Total	120,422
Accumulated Depreciation	(47,323)
Inpatient [Member] | Arizona [Member]
Summary of Company's investment
Number of owned real estate properties	1
Land and Land Held for Development	3,641	[1]
Buildings, Improvements, Lease Intangibles and CIP	12,371
Personal Property	0
Gross real estate asset, Total	16,012
Accumulated Depreciation	(1,127)
Other [Member]
Summary of Company's investment
Number of owned real estate properties	10
Land and Land Held for Development	1,901	[1]
Buildings, Improvements, Lease Intangibles and CIP	43,853
Personal Property	636
Gross real estate asset, Total	46,390
Accumulated Depreciation	(23,096)
Other [Member] | Indiana [Member]
Summary of Company's investment
Number of owned real estate properties	1
Land and Land Held for Development	96	[1]
Buildings, Improvements, Lease Intangibles and CIP	3,662
Personal Property	32
Gross real estate asset, Total	3,790
Accumulated Depreciation	(2,247)
Other [Member] | Michigan [Member]
Summary of Company's investment
Number of owned real estate properties	5
Land and Land Held for Development	193	[1]
Buildings, Improvements, Lease Intangibles and CIP	12,729
Personal Property	183
Gross real estate asset, Total	13,105
Accumulated Depreciation	(7,585)
Other [Member] | Tennessee [Member]
Summary of Company's investment
Number of owned real estate properties	1
Land and Land Held for Development	253	[1]
Buildings, Improvements, Lease Intangibles and CIP	7,213
Personal Property	408
Gross real estate asset, Total	7,874
Accumulated Depreciation	(1,833)
Other [Member] | Virginia [Member]
Summary of Company's investment
Number of owned real estate properties	2
Land and Land Held for Development	1,178	[1]
Buildings, Improvements, Lease Intangibles and CIP	10,656
Personal Property	5
Gross real estate asset, Total	11,839
Accumulated Depreciation	(5,529)
Other [Member] | Alabama [Member]
Summary of Company's investment
Number of owned real estate properties	1
Land and Land Held for Development	181	[1]
Buildings, Improvements, Lease Intangibles and CIP	9,593
Personal Property	8
Gross real estate asset, Total	9,782
Accumulated Depreciation	$ (5,902)

[1] Includes hand held for development.