Fair Value Measurements - Fair Value Assets Measured on a Non-recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	$ 1,357	$ 1,114	$ 1,006
Development projects in progress		3,791
Land held for sale		325
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	0	0	0
Development projects in progress		0
Land held for sale		0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	1,357	1,114	1,006
Development projects in progress		0
Land held for sale		0
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	0	0	$ 0
Development projects in progress		3,791
Land held for sale		$ 325
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Land held for sale	642
Fair Value, Measurements, Nonrecurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Land held for sale	0
Fair Value, Measurements, Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Land held for sale	0
Fair Value, Measurements, Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Land held for sale	$ 642