Financial Instruments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012 Derivative	Dec. 31, 2011	Dec. 31, 2012 Treasury locks [Member]	Dec. 31, 2012 Eight interest rate swaps entered in 2012 [Member]	Nov. 30, 2012 4.625% senior unsecured notes [Member]	Jun. 30, 2012 4.625% senior unsecured notes [Member]
Derivative [Line Items]
Aggregate Notional Amount	$ 632,800,000	$ 284,100,000	$ 200,000,000	$ 450,000,000
Principal amount of Senior Notes	450,000,000				150,000,000	300,000,000
Payment to the counter party			4,700,000
Unrealized loss of hedging instrument	8,300,000	3,700,000
Approximate fair value of notes	250,700,000	90,600,000
Carrying amount of notes	250,400,000	91,000,000
Tax Increment Financing Bonds ("TIF Bonds")	5,200,000	6,400,000
Derivative financial instruments	17,100,000	8,800,000
Number of interest rate derivatives held	10
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months, net	$ (7,300,000)