Indebtedness - Schedule of Indebtedness (Parenthetical) (Detail) - Jun. 30, 2015	Total
Unsecured Bank Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity	2020
Interest Rate Swap [Member] | Unsecured Bank Term Loan [Member]
Debt Instrument [Line Items]
Effective blended interest rate	2.69%
Minimum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity	2017
Maximum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity	2022