Debt Obligations (Details Textuals) (USD $) In Millions, unless otherwise specified				6 Months Ended			6 Months Ended
	Jun. 30, 2014 Secured Debt [Member]	Jun. 30, 2013 Secured Debt [Member]	Jun. 30, 2014 Unsecured Debt [Member] Three Year Term Loan [Member]	Jun. 30, 2014 Unsecured Debt [Member] Letter of Credit [Member]	Jun. 30, 2014 Unsecured Debt [Member] Line of Credit [Member]	Jun. 30, 2014 Unsecured Debt [Member] Four Year Term Loan [Member]	Jun. 30, 2014 Unsecured Debt [Member] Seven Year Term Loan [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate	5.73%	6.64%
Debt Instrument, Basis Spread on Variable Rate				1.50%
Letters of Credit Outstanding, Amount				$ 1.5
Line of Credit Facility, Remaining Borrowing Capacity					598.5
Debt Instrument, Face Amount			150.0			250.0	200.0
Line of Credit Facility, Option for Additional Borrowing Capacity subject to customary conditions and limitations					$ 200.0
Declining prepayment penalty after Three Years							1.00%
Derivative, Average Fixed Interest Rate			2.596%				3.623%