Derivatives (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Schedule of interest rate swap and cap contracts
Notional Amount	$ 233,669
Fair Value	(1,735)	(2,284)
Interest Rate Swap 3.32% [Member]
Schedule of interest rate swap and cap contracts
Date Entered	Mar. 28, 2008
Effective Date	Mar. 28, 2008
End Date	Mar. 27, 2013
Pay Fixed Rate	3.32%
Receive Floating Rate Index	1 month LIBOR
Notional Amount	33,062
Fair Value	(742)	(1,156)
Interest Rate Swap 1.62% [Member]
Schedule of interest rate swap and cap contracts
Date Entered	Jan. 16, 2009
Effective Date	Jan. 13, 2009
End Date	Jan. 13, 2012
Pay Fixed Rate	1.62%
Receive Floating Rate Index	1 month LIBOR
Fair Value	0	(10)
Interest Rate Swap 0.63% [Member]
Schedule of interest rate swap and cap contracts
Date Entered	Aug. 19, 2010
Effective Date	Aug. 31, 2010
End Date	Mar. 27, 2012
Pay Fixed Rate	0.63%
Receive Floating Rate Index	1 month LIBOR
Fair Value	0	(22)
Interest Rate Swap 0.94% [Member]
Schedule of interest rate swap and cap contracts
Date Entered	Oct. 15, 2010
Effective Date	Nov. 01, 2010
End Date	Apr. 23, 2013
Pay Fixed Rate	0.94%
Receive Floating Rate Index	1 month LIBOR
Notional Amount	29,727
Fair Value	(157)	(181)
Interest Rate Swap 0.91%(1) [Member]
Schedule of interest rate swap and cap contracts
Date Entered	Jan. 07, 2011
Effective Date	Jan. 07, 2011
End Date	Jan. 13, 2013
Pay Fixed Rate	0.91%
Receive Floating Rate Index	1 month LIBOR
Notional Amount	26,221
Fair Value	(86)	(121)
Interest Rate Swap 0.91%(2) [Member]
Schedule of interest rate swap and cap contracts
Date Entered	Jan. 07, 2011
Effective Date	Jan. 07, 2011
End Date	Jan. 13, 2013
Pay Fixed Rate	0.91%
Receive Floating Rate Index	1 month LIBOR
Notional Amount	22,809
Fair Value	(75)	(105)
Interest Rate Swap 1.575% [Member]
Schedule of interest rate swap and cap contracts
Date Entered	Apr. 28, 2011
Effective Date	May 03, 2011
End Date	Sep. 30, 2012
Pay Fixed Rate	1.575%
Receive Floating Rate Index	1 month LIBOR
Notional Amount	56,702
Fair Value	(181)	(481)
Interest Rate Swap 0.79% [Member]
Schedule of interest rate swap and cap contracts
Date Entered	Sep. 01, 2011
Effective Date	Sep. 29, 2012
End Date	Sep. 29, 2014
Pay Fixed Rate	0.79%
Receive Floating Rate Index	1 month LIBOR
Notional Amount	56,702
Fair Value	(421)	(130)
Interest Rate Swap 1.037% [Member]
Schedule of interest rate swap and cap contracts
Date Entered	Oct. 14, 2011
Effective Date	Oct. 14, 2011
End Date	Oct. 22, 2013
Pay Fixed Rate	1.037%
Receive Floating Rate Index	1 month LIBOR
Notional Amount	8,446
Fair Value	$ (73)	$ (78)