Debt Covenants and Events of Default - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Debt Instrument [Line Items]
Long-term debt	$ 176,011	$ 178,453	$ 228,306
Current maturities of long-term debt	$ 47,298	46,048	14,796
Covenant compliance	As of March 31, 2018, we were in compliance with all covenants contained in the Credit Agreement and related to the note purchase agreement governing our 2019 Notes. We are not aware of any non-compliance by any of our unconsolidated real estate entities with the covenants contained in their debt agreements.
Term Loan [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 88,800
Long-term debt	81,300	83,800	88,800
Short term portion of term loan	7,500	6,200	5,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	200,000
Revolving credit agreement	55,000	55,000	30,000
Line of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	288,800
Term Loan Sublimit for Letters of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	100,000
Senior Notes [Member] | 2019 Notes [Member]
Debt Instrument [Line Items]
Long-term debt	40,000	40,000	110,000
Debt instrument, face amount	$ 80,000	80,000	120,000
Debt instrument, interest rate, stated percentage	6.11%
Current maturities of long-term debt	$ 40,000	$ 40,000	10,000
Senior Notes [Member] | 2019 Notes [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Scheduled installment payments			$ 30,000