Outstanding Interest Rate Derivatives Designated as Cash Flow Hedges of Interest Rate Risk (Detail) (Designated as Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2013 Contract
Interest Rate Caps
Derivative [Line Items]
Derivative, Number of Instruments Held	12
Notional	$ 224,600
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held	18
Notional	559,000
Interest Rate Forward Swap [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held	3
Notional	$ 150,000

Aggregate notional amount of interest rate derivatives, which relates to the currency amount specified in the interest rate derivative instruments.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959

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