Summary of Significant Accounting Policies (Details 2) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Fair value of assets and liabilities measured at fair value on a recurring and non-recurring basis
Percentage of debt having fixed interest rates	68.20%	69.60%
Carrying value of secured debt	$ 1,300,869,000	$ 1,363,389,000
Assets:
Interest rate cap derivative agreements	57,000	48,000
Accounts Receivable
Allowance for doubtful accounts	200,000	200,000
Total at the end of the period
Assets:
Interest rate cap derivative agreements	57,000	48,000
Life insurance policy	1,544,000	1,494,000
Total assets	1,601,000	1,542,000
Liabilities:
Interest rate swap derivative agreements	1,488,000	1,636,000
Retirement benefit agreement	1,544,000	1,494,000
Total liabilities	3,032,000	3,130,000
Level 2
Assets:
Interest rate cap derivative agreements	57,000	48,000
Life insurance policy	1,544,000	1,494,000
Total assets	1,601,000	1,542,000
Liabilities:
Interest rate swap derivative agreements	1,488,000	1,636,000
Retirement benefit agreement	1,544,000	1,494,000
Total liabilities	3,032,000	3,130,000
Level 3
Fair value of assets and liabilities measured at fair value on a recurring and non-recurring basis
Weighted average cost of debt (as a percent)	5.50%
Fair value of debt	1,300,000,000	1,300,000,000
Robert A. Alter
Fair value of assets and liabilities measured at fair value on a recurring and non-recurring basis
Split life insurance policy	5,000,000
Number of installments to be paid out under the Retirement Benefit Agreement	10
Amount paid under the Retirement Benefit Agreement	400,000
Robert A. Alter | Level 2
Assets:
Life insurance policy	1,500,000	1,500,000
Liabilities:
Retirement benefit agreement	1,500,000	1,500,000
Interest Rate Cap Agreement
Fair value of assets and liabilities measured at fair value on a recurring and non-recurring basis
Number of derivative agreements	2	2
Interest Rate Swap Agreement
Fair value of assets and liabilities measured at fair value on a recurring and non-recurring basis
Number of derivative agreements	1	1
Liabilities:
Interest rate swap derivative agreements	$ 1,500,000	$ 1,600,000