Derivatives (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended				6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Forward Contracts [Member] instrument	Apr. 30, 2013 Forward Contracts [Member]	Jun. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member]	Jun. 30, 2012 Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Interest rate cash flow hedge liability, fair value						$ 3,156
Number of interest rate derivatives held					4
Derivative, Notional Amount					240,000
Amount of cash flow hedge reported in AOCI						(3,141)
Fair value of interest rate hedges recognized in other comprehensive income			8,656
Interest expense	23,394	19,569	45,221	39,387			178	114
Interest rate hedges gain (loss) to be reclassified into interest expense over next 12 months	$ 557		$ 557