Fair Value Measures And Other Financial Instruments (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended		1 Months Ended
	Sep. 30, 2012	Dec. 31, 2011 Three Interest Rate Swap [Member]	Jan. 31, 2012 Fourth Interest Rate Swap [Member]	Jan. 31, 2012 Term Loan Borrowings Fully Drawn [Member]	Sep. 30, 2012 Unsecured Bank Term Loan [Member]	Sep. 30, 2012 Fixed Rate Debt [Member]	Dec. 31, 2011 Fixed Rate Debt [Member]	Sep. 30, 2012 Variable Rate Debt [Member]	Dec. 31, 2011 Variable Rate Debt [Member]	Sep. 30, 2012 Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2011 Fair Value, Inputs, Level 2 [Member]	Sep. 30, 2012 Fair Value, Inputs, Level 3 [Member] Atlanta Condominium Project [Member]	Dec. 31, 2011 Fair Value, Inputs, Level 3 [Member] Atlanta Condominium Project [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notional amounts		$ 230,000	$ 70,000
Derivative, fixed interest rate		1.55%	1.50%	3.44%
LIBOR rate			One-month
Reduction in blended interest rate					3.24%
Net liabilities										12,648	2,641
Accumulated comprehensive income (loss) to interest expense, future periods	4,007
Termination payment	12,801
Fair value of debt						800,906	885,455	297,277	137,495
Carrying value of debt						736,492	835,443	300,000	135,000
Fair value of contractual obligation												$ 3,163	$ 5,348