Bradley Agreement (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) parking_space	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2002 USD ($)
Deficiency payments:
Balance at the beginning of the year	$ 13,300,000	$ 14,600,000
Deficiency payments made	100,000	0
Deficiency repayment received	(1,800,000)	(1,300,000)
Balance at the end of the year	11,600,000	13,300,000	$ 14,600,000
Compensation
Management fees	$ 0	0	$ 0
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 | parking_space	3,500
Annual minimum guaranteed payment to the State by the trustee	$ 11,000,000	10,800,000
Maximum premium percentage on initial deficiency payment	10.00%
Deficiency payments:
Net deficiency payments received (paid)	$ 1,700,000	(1,300,000)
Interest income on deficiency payment received from trustee	400,000	500,000
Premium income on deficiency payment received from trustee	200,000	100,000
Estimated accrued deficiency payments	$ 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	$ 15,700,000	$ 14,700,000
Bradley International Airport parking facilities operating agreement | Minimum
Agreement
Annual minimum guaranteed payment to the State by the trustee				$ 8,300,000
Bradley International Airport parking facilities operating agreement | Maximum
Agreement
Annual minimum guaranteed payment to the State by the trustee	13,200,000
Bradley International Airport parking facilities operating agreement | State of Connecticut special facility revenue bonds | Minimum
Agreement
Annual principal and interest on revenue bonds				$ 3,600,000
Bradley International Airport parking facilities operating agreement | State of Connecticut special facility revenue bonds | Maximum
Agreement
Annual principal and interest on revenue bonds	$ 4,500,000