Interest Rate Derivative Instruments (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Feb. 29, 2012	Feb. 08, 2012
Derivative [Line Items]
Unrealized gains or losses on cash flow hedge derivative effective portion			$ 0	$ 200
Interest expense related to payments on interest rate swaps	$ 4,799	$ 2,208	10,141	4,273
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative instruments, notional amount	0		0
Interest expense related to payments on interest rate swaps	$ 0	$ 200	$ 0	$ 300
Cash Flow Hedging [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative inception date			Feb. 08, 2012
Derivative maturity date			Sep. 28, 2014
Derivative instruments, notional amount					$ 150,000	$ 150,000