Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Fair value of assets and liabilities measured on a recurring basis
Fair Value, Beginning Balance			$ 53,804	$ 51,177
Investment accretion included in interest income			2,833	2,556
Unrealized losses included in interest expense			(36)	(36)
Losses on interest rate swaps reclassified into interest expense from accumulated other comprehensive loss	421	422	1,265	1,258
Unrealized gains (losses) included in equity and partners’ capital			(2,106)	(3,017)
Fair Value, Ending Balance	55,760	51,938	55,760	51,938
Fair Value, Inputs, Level 2 [Member] | Available for sale [Member]
Fair value of assets and liabilities measured on a recurring basis
Fair Value, Beginning Balance			58,408	59,145
Investment accretion included in interest income			2,833	2,556
Unrealized losses included in interest expense
Losses on interest rate swaps reclassified into interest expense from accumulated other comprehensive loss
Unrealized gains (losses) included in equity and partners’ capital			(618)	(4,440)
Fair Value, Ending Balance	60,623	57,261	60,623	57,261
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Fair value of assets and liabilities measured on a recurring basis
Fair Value, Beginning Balance			(4,604)	(7,968)
Investment accretion included in interest income
Unrealized losses included in interest expense			(36)	(36)
Losses on interest rate swaps reclassified into interest expense from accumulated other comprehensive loss			1,265	1,258
Unrealized gains (losses) included in equity and partners’ capital			(1,488)	1,423
Fair Value, Ending Balance	$ (4,863)	$ (5,323)	$ (4,863)	$ (5,323)