Investment in Direct Financing Lease - Narrative (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Percentage of term exceeding useful life of one office tower	75.00%
Allowance for losses related to our direct financing lease	$ 0	$ 0

The estimate of contractual payments on direct financing leases that are probable of not being collected as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 4

-Subparagraph (a)(1)(ii)

-URI http://asc.fasb.org/extlink&oid=25496975&loc=d3e45377-112738

Name:	us-gaap_CapitalLeasesNetInvestmentInDirectFinancingLeasesAllowanceForUncollectibleMinimumLeasePayments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant