XML 64 R46.htm IDEA: XBRL DOCUMENT v3.8.0.1
Revolving Credit Facilities - Additional Information (Detail) - Unsecured Debt [Member] - Revolving Credit Facility [Member]
3 Months Ended
Mar. 31, 2018
USD ($)
Debt Instrument [Line Items]  
Covenant compliance The Company was in compliance with these financial covenants at March 31, 2018.
LIBOR [Member]  
Debt Instrument [Line Items]  
Specified spread line of credit facility 1.20%
Alternative Base Rate [Member]  
Debt Instrument [Line Items]  
Specified spread line of credit facility 0.20%
J.P. Morgan Chase Bank, N.A., Wells Fargo Securities, LLC, Citizens Bank, N.A., RBC Capital Markets and U.S. Bank National Association [Member]  
Debt Instrument [Line Items]  
Line of credit facility competitive bid option on periodic interest rates up to 50% of the facility
Facility fee 0.25%
Revolving credit facility maturity extension option two six-month options to extend the maturity to September 2022 upon the Company’s request
J.P. Morgan Chase Bank, N.A., Wells Fargo Securities, LLC, Citizens Bank, N.A., RBC Capital Markets and U.S. Bank National Association [Member] | Maximum [Member]  
Debt Instrument [Line Items]  
Unsecured revolving credit facility borrowing capacity $ 950,000,000
Accordion feature 1,450,000,000
PNC Bank National Association [Member]  
Debt Instrument [Line Items]  
Unsecured revolving credit facility $ 50,000,000