Derivatives (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Interest expense [Member] Interest rate swap [Member]	Jun. 30, 2013 Interest expense [Member] Interest rate swap [Member]	Jun. 30, 2014 Interest expense [Member] Interest rate swap [Member]	Jun. 30, 2013 Interest expense [Member] Interest rate swap [Member]	Jun. 30, 2014 Interest expense [Member] Fixed-rate debt [Member]	Jun. 30, 2013 Interest expense [Member] Fixed-rate debt [Member]	Jun. 30, 2014 Interest expense [Member] Fixed-rate debt [Member]	Jun. 30, 2013 Interest expense [Member] Fixed-rate debt [Member]	Jun. 30, 2014 Prepaid Expenses and Other Current Assets [Member]	Dec. 31, 2013 Prepaid Expenses and Other Current Assets [Member]	Jun. 30, 2014 Direct Financing Leases and Other Assets [Member]	Dec. 31, 2013 Direct Financing Leases and Other Assets [Member]	Jun. 30, 2014 Other Noncurrent Liabilities [Member]	Dec. 31, 2013 Other Noncurrent Liabilities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Fair Value Hedge Asset at Fair Value													$ 1,834	$ 0	$ 6,162	$ 9,333
Location and amount of gains (losses) on derivative instruments and related hedged items
Derivative: Interest rate swap					1,667	(3,586)	(316)	(6,367)
Hedged item: Fixed-rate debt									(1,667)	3,586	316	6,367
Total	0	0	0	0
Interest Rate Derivative Liabilities, at Fair Value																	$ 141	$ 1,162