Summary of Significant Accounting Policies (Details)			3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) item	Dec. 31, 2014 USD ($) item	Jun. 30, 2015 USD ($) item	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) item	Jun. 30, 2014 USD ($)	Dec. 31, 2011 item
Fair value of assets and liabilities measured at fair value on a recurring and non-recurring basis
Impairment loss on continuing operations			$ 0	$ 0	$ 0	$ 0
Goodwill impairment loss			$ 0	$ 0	$ 0	$ 0
Percentage of debt having fixed interest rates	69.40%	71.60%	69.40%		69.40%
Robert A. Alter
Liabilities:
Number of installments to be paid out under the Retirement Benefit Agreement | item							10
Amount paid under the Retirement Benefit Agreement	$ 1,000,000		$ 1,000,000		$ 1,000,000
Total at the end of the period
Assets:
Life insurance policy	1,005,000	$ 1,198,000	1,005,000		1,005,000
Total assets	1,005,000	1,198,000	1,005,000		1,005,000
Liabilities:
Retirement benefit agreement	1,005,000	1,198,000	1,005,000		1,005,000
Level 2
Assets:
Life insurance policy	1,005,000	1,198,000	1,005,000		1,005,000
Total assets	1,005,000	1,198,000	1,005,000		1,005,000
Liabilities:
Retirement benefit agreement	$ 1,005,000	$ 1,198,000	1,005,000		1,005,000
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)	4.50%	4.50%
Fair value of debt	$ 1,300,000,000	$ 1,400,000,000	$ 1,300,000,000		$ 1,300,000,000
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 | item	2	2	2		2