Debt - Principal Payments Due on Consolidated Debt during Each of Next Five Years and Thereafter (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Remainder of 2014	$ 1,808
2015	275,981
2016	20,040
2017	147,175
2018	369,418
Thereafter	1,126,556
Total principal payments	1,940,978
Unamortized premium on assumed debt	4,919
Total	1,945,897	1,876,631
Lines of Credit [Member]
Debt Instrument [Line Items]
Remainder of 2014	0
2015	223,000
2016	0
2017	85,000
2018	0
Thereafter	0
Total principal payments	308,000
Unamortized premium on assumed debt	0
Total	308,000
Unsecured Term Loans [Member]
Debt Instrument [Line Items]
Remainder of 2014	0
2015	0
2016	0
2017	0
2018	200,000
Thereafter	300,000
Total principal payments	500,000
Unamortized premium on assumed debt	0
Total	500,000	500,000
Mortgage Notes [Member]
Debt Instrument [Line Items]
Remainder of 2014	1,808
2015	52,981
2016	20,040
2017	62,175
2018	169,418
Thereafter	826,556
Total principal payments	1,132,978
Unamortized premium on assumed debt	4,919
Total	$ 1,137,897