Summary of Significant Accounting Policies - Additional Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
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
Accounting Policies [Abstract]
Distributions from taxable income									100.00%
Share-based compensation expense	$ 1,020us-gaap_ShareBasedCompensation	$ 890us-gaap_ShareBasedCompensation	$ 842us-gaap_ShareBasedCompensation	$ 860us-gaap_ShareBasedCompensation	$ 701us-gaap_ShareBasedCompensation	$ 637us-gaap_ShareBasedCompensation	$ 627us-gaap_ShareBasedCompensation	$ 629us-gaap_ShareBasedCompensation	$ 3,612us-gaap_ShareBasedCompensation	$ 2,594us-gaap_ShareBasedCompensation	$ 1,920us-gaap_ShareBasedCompensation

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Name:	us-gaap_ShareBasedCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration