Real Estate and Lending Activities - Gilbert and Florence Facilities - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended
Mar. 31, 2017	Mar. 31, 2018
Business Acquisition [Line Items]
Gain offset by non-cash charges	$ 0.6
Gilbert and Florence Facilities [Member]
Business Acquisition [Line Items]
Gain offset by non-cash charges		$ 1.1
Total budgeted investment		$ 38.1

Sum of the carrying amounts as of the balance sheet date of all investments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(h))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Name:	us-gaap_Investments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant