Bradley Agreement (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) item	Jun. 30, 2014 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Deficiency payments
Interest income on deficiency payment received from trustee			$ 256
Deficiency payments
Deficiency payments
Balance at the beginning of the year			13,327		$ 13,327
Deficiency payments made			38
Deficiency repayment received			(837)
Balance at the end of the year	$ 12,528		$ 12,528			$ 13,327
Bradley International Airport parking facilities operating agreement
Agreement
Agreement period with the State of Connecticut for operation of parking spaces			25 years
Number of garage parking spaces at Bradley International Airport operated | item			3,500
Annual minimum guaranteed payment to the State by the trustee						10,815
Deficiency payments
Maximum premium percentage on initial deficiency payment			10.00%
Net deficiency repayment received (paid)	795	$ 957	$ 799	$ 1,050
Interest income on deficiency payment received from trustee	213
Premium income on deficiency payment received from trustee	71	$ 104	79	(117,000)
Estimated accrued deficiency payments	0		$ 0			0
Compensation
Management fee apportioned to the entity (as a percent)			60.00%
Management fee apportioned to an un-affiliated entity (as a percent)			40.00%
Unrecognized cumulative management fees	15,233		$ 15,233			$ 14,733
Management Fees			0	$ 0
Bradley International Airport parking facilities operating agreement | Forecast
Agreement
Annual minimum guaranteed payment to the State by the trustee					$ 11,042
Bradley International Airport parking facilities operating agreement | Minimum
Agreement
Annual minimum guaranteed payment to the State by the trustee			8,300
Bradley International Airport parking facilities operating agreement | Maximum
Agreement
Annual minimum guaranteed payment to the State by the trustee			13,200
Bradley International Airport parking facilities operating agreement | State of Connecticut special facility revenue bonds | Minimum
Agreement
Annual principal and interest on revenue bonds	3,600		3,600
Bradley International Airport parking facilities operating agreement | State of Connecticut special facility revenue bonds | Maximum
Agreement
Annual principal and interest on revenue bonds	$ 4,500		$ 4,500