Related Party Transactions - Summary of Fees and Expenses Incurred by Company (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2014
Related Party Transactions [Abstract]
Development acquisition fees	$ 2.6
Asset management fees paid in connection with dispositions	$ 2.6

The amount of asset management fees paid to a related party in connection with a disposition, which may involve a sale of one or more assets or a sale, merger, or other transaction.

No definition available.

Name:	ck0001464720_AssetManagementFeesPaidToRelatedPartyInConnectionWithDisposition
Namespace Prefix:	ck0001464720_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration