Debt - Long-Term Debt Maturities (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Maturities Of Long Term Debt [Line Items]
Debt maturities	$ 800.0
Consolidated Entities [Member]
Maturities Of Long Term Debt [Line Items]
Consolidated investee credit facility included in debt	17.6
Debt maturities	117.0
Consolidated Entities [Member] \| Credit Facilities [Member]
Maturities Of Long Term Debt [Line Items]
Debt maturities	64.4
Consolidated Entities [Member] \| Secured Mortgage Debt [Member]
Maturities Of Long Term Debt [Line Items]
Debt maturities	$ 34.7

Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 47

-Paragraph 10

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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