Amendment of Revolving Credit Facility Amendment of Revolving Credit Facility (Details) (USD $)	9 Months Ended		0 Months Ended	9 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	May 17, 2013 Revolving Credit Facility London Interbank Offered Rate (LIBOR)	Sep. 30, 2013 Revolving Credit Facility London Interbank Offered Rate (LIBOR)	Oct. 31, 2010 Revolving Credit Facility London Interbank Offered Rate (LIBOR)	Sep. 30, 2013 Maximum Revolving Credit Facility London Interbank Offered Rate (LIBOR)	Sep. 30, 2013 Minimum Revolving Credit Facility London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount			$ 500,000,000		$ 375,000,000
Debt Instrument additional amount			225,000,000
Loan origination fees	$ 2,038,000	$ 0	$ 2,000,000
Debt Instrument, Description of Variable Rate Basis				LIBOR
Debt Instrument, Basis Spread on Variable Rate						3.00%	1.125%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage						0.45%	0.175%
Line of Credit Facility, Covenant Terms, Interest Coverage Ratio							3.0
Line of Credit Facility, Covenant Terms, Leverage Ratio						5.0	4.5
Line of Credit Facility, Covenant Terms,SeniorSecuredLeverage Ratio						3.5