Derivative Financial Instruments - Additional Information (Detail) (USD $)	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Derivative [Line Items]
Notional amount	$ 245,000,000
Realized loss reclassified from accumulated other comprehensive loss to interest expense	(3,707,000)	(9,841,000)
Estimated payments to be made under interest rate swaps	4,900,000
Fair value of interest rate swap agreements	$ 16,493,000		$ 10,748,000

Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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