Retirement and Postretirement Benefits Other than Pension Plans - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013
REIT Conversion [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net settlement loss	$ 600	$ 600
Corporate Operating Expenses [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net settlement loss	700	700
Pension Plans, Defined Benefit [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net settlement loss	$ 1,290	$ 1,290