Schedule of Interest Rate Swap Agreements on Accumulated Other Comprehensive Income (Details) - Interest Rate Swap - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Beginning balance	$ (7,325)	$ (63,567)	$ (30,042)	$ (111,174)
Reclassification of net losses to the income statement	5,433	19,806	28,150	67,413
Ending balance	$ (1,892)	$ (43,761)	$ (1,892)	$ (43,761)