Retirement and Postretirement Benefits Other than Pension Plans - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
REIT Conversion [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net settlement loss			$ 700,000
Corporate Operating Expenses [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net settlement loss	200,000		800,000
Pension Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net settlement loss	188,000		1,478,000
Expected contribution to defined benefit pension plan		$ 1,900,000