Equity and Capital Equity and Capital - Common Stock (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Aug. 10, 2013 Maximum [Member]	Jun. 30, 2014 Accumulated Other Comprehensive Income (Loss) [Member]	Dec. 31, 2013 Accumulated Other Comprehensive Income (Loss) [Member]	Jun. 30, 2013 Accumulated Other Comprehensive Income (Loss) [Member]	Dec. 31, 2012 Accumulated Other Comprehensive Income (Loss) [Member]	Jun. 30, 2014 Loss on Settlement of Derivative Instruments [Member]	Dec. 31, 2013 Loss on Settlement of Derivative Instruments [Member]	Jun. 30, 2013 Loss on Settlement of Derivative Instruments [Member]	Dec. 31, 2012 Loss on Settlement of Derivative Instruments [Member]	Jun. 30, 2014 Fair Value of Derivative Instruments [Member]	Dec. 31, 2013 Fair Value of Derivative Instruments [Member]	Jun. 30, 2013 Fair Value of Derivative Instruments [Member]	Dec. 31, 2012 Fair Value of Derivative Instruments [Member]
Class of Stock [Line Items]
Document Fiscal Year Focus			2014
Amount reclassified from accumulated other comprehensive loss	$ (2,275,000)	$ (2,366,000)	$ (4,749,000)	$ (4,732,000)
Shares issued		873	0	1,869
Accumulated other comprehensive loss						(36,412,000)	(17,404,000)	(31,319,000)	(57,715,000)	(48,018,000)	(52,542,000)	(57,267,000)	(61,991,000)	10,694,000	35,138,000	25,948,000	4,276,000
Equity Issuances, Amount Available for Issuance	200,000,000		200,000,000		200,000,000
Weighted Average Price Per Share		$ 54.22		$ 53.37
Net proceeds from common stock issuance		47,377,000		99,774,000
Payments for Commissions		$ 709,000		$ 1,496,000