Indebtedness - Schedule of Indebtedness (Parenthetical) (Detail)	9 Months Ended
	Sep. 30, 2015
Senior Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity	2017
Senior Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity	2022
Unsecured Bank Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity	2020
Unsecured Bank Term Loan [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Effective blended interest rate	2.69%