Financing Activity - Applicable Credit Spread Over Libor at Various Leverage Levels (Detail)	3 Months Ended
	Mar. 31, 2018
Minimum [Member]
Schedule Of Maximum Leverage Ratio [Line Items]
Capitalization Rates	6.50%
Maximum [Member]
Schedule Of Maximum Leverage Ratio [Line Items]
Capitalization Rates	7.50%
Ratio One [Member] | London Interbank Offered Rate (LIBOR) [Member] | 2013 Revolving Credit Facility [Member]
Schedule Of Maximum Leverage Ratio [Line Items]
Stated Interest Rate	1.20%
Ratio One [Member] | London Interbank Offered Rate (LIBOR) [Member] | Term Loan [Member]
Schedule Of Maximum Leverage Ratio [Line Items]
Stated Interest Rate	1.35%
Ratio Two [Member] | London Interbank Offered Rate (LIBOR) [Member] | 2013 Revolving Credit Facility [Member]
Schedule Of Maximum Leverage Ratio [Line Items]
Stated Interest Rate	1.25%
Ratio Two [Member] | London Interbank Offered Rate (LIBOR) [Member] | Seven Year Term Loan [Member]
Schedule Of Maximum Leverage Ratio [Line Items]
Stated Interest Rate	1.45%
Ratio Three [Member] | London Interbank Offered Rate (LIBOR) [Member] | 2013 Revolving Credit Facility [Member]
Schedule Of Maximum Leverage Ratio [Line Items]
Stated Interest Rate	1.30%
Ratio Three [Member] | London Interbank Offered Rate (LIBOR) [Member] | Seven Year Term Loan [Member]
Schedule Of Maximum Leverage Ratio [Line Items]
Stated Interest Rate	1.60%
Ratio Four [Member] | London Interbank Offered Rate (LIBOR) [Member] | 2013 Revolving Credit Facility [Member]
Schedule Of Maximum Leverage Ratio [Line Items]
Stated Interest Rate	1.55%
Ratio Four [Member] | London Interbank Offered Rate (LIBOR) [Member] | Seven Year Term Loan [Member]
Schedule Of Maximum Leverage Ratio [Line Items]
Stated Interest Rate	1.90%