Mortgage Notes Payable (National Institute of Health) (Detail) (USD $)	Sep. 30, 2014		Dec. 31, 2013		Sep. 30, 2013	Nov. 05, 2013	Jun. 12, 2014
Impaired Assets to be Disposed of by Method Other than Sale [Line Items]
Mortgage notes payable, net	$ 3,782,407,000		$ 1,301,114,000	[1]	$ 272,015,000
Mortgages [Member]
Impaired Assets to be Disposed of by Method Other than Sale [Line Items]
Mortgage notes payable, net	4,237,464,000	[2]	1,258,661,000
CapLease [Member]
Impaired Assets to be Disposed of by Method Other than Sale [Line Items]
Building, historical cost						40,000,000
Bethesda Maryland [Member] | CapLease [Member]
Impaired Assets to be Disposed of by Method Other than Sale [Line Items]
Area leased (in square feet)	9,133
Net rentable area (in square feet)	207,055
Percentage of square footage leased	4.40%
Bethesda Maryland [Member] | CapLease [Member] | Mortgages [Member]
Impaired Assets to be Disposed of by Method Other than Sale [Line Items]
Debt issued amount							65,200,000
Mortgage notes payable, net							$ 53,800,000
Interest rate, stated percentage	5.32%

[1] For discussion on the restatement adjustments, see Note 2 - Restatement of Previously Issued Consolidated Financial Statements.

[2] Includes $542.8 million of mortgage notes held for sale.