Loans Payable, Senior Notes and Mortgage Company Loan Facility Senior Notes Payable (Details Textual 4) $ in Millions	Jan. 31, 2017 USD ($) debtissuances
Senior Note Payable (Textual) [Abstract]
Number of issuances of senior debt \| debtissuances	8
Senior Notes [Member]
Senior Note Payable (Textual) [Abstract]
Debt Instrument, Face Amount \| $	$ 2,707

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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