Debt Obligations (Details Textuals) (USD $)	0 Months Ended	3 Months Ended		9 Months Ended
	Sep. 16, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Debt Instrument [Line Items]
Extinguishment of Debt, Amount				$ 117,755,000
Loss on early extinguishment of debt	2,606,000	(2,606,000)	(11,000)	(2,606,000)	(1,127,000)
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate		5.73%	6.64%	5.73%	6.64%
Unsecured Debt [Member] | Three and Four Year Term Loan [Member]
Debt Instrument [Line Items]
Write off of Deferred Debt Issuance Cost	300,000
Unsecured Debt [Member] | Note 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		250,000,000		250,000,000
Debt instrument, Unamortized discount, Percent of face amount	99.388%
Debt instrument, Yield to maturity	4.175%
Debt instrument, Yield to maturity spread at time of pricing	1.70%
Unsecured Debt [Member] | Note 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		250,000,000		250,000,000
Debt instrument, Unamortized discount, Percent of face amount	99.191%
Debt instrument, Yield to maturity	4.625%
Debt instrument, Yield to maturity spread at time of pricing	2.15%
Unsecured Debt [Member] | Notes 2024 and 2029 [Member]
Debt Instrument [Line Items]
Proceeds from Notes Payable	492,900,000
Unsecured Debt [Member] | Three Year Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	150,000,000
Unsecured Debt [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate				1.50%
Letters of Credit Outstanding, Amount		2,800,000		2,800,000
Unsecured Debt [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity		597,200,000		597,200,000
Unsecured Debt [Member] | Four Year Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption, Description	1,026.88 per $1,000
Extinguishment of Debt, Amount	75,100,000
Debt Instrument, Face Amount		250,000,000		250,000,000
Unsecured Debt [Member] | 2015 7.500% Notes
Debt Instrument [Line Items]
Debt Instrument, Redemption, Description	$1,070.24 per $1,000
Extinguishment of Debt, Amount	42,700,000
Debt Instrument, Face Amount		250,000,000		250,000,000
Unsecured Debt [Member] | Seven Year Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 200,000,000		$ 200,000,000
Declining prepayment penalty after Three Years				1.00%
Derivative, Average Fixed Interest Rate		3.623%		3.623%