Equity and Capital (Tables)

12 Months Ended

Dec. 31, 2013

Terms and Conditions of Preferred Stock (details) [Abstract]

Schedule of Market Equity Distributions [Table Text Block]

During the year ended December 31, 2013, the following shares were issued under the ATM equity program (in thousands, except share data):

		2013	2012
Shares issued		1,899	443
Weighted average price per share	$	53.35	49.70
Gross proceeds	$	101,342	22,007
Commissions	$	1,521	331
Issuance costs	$	68	134

Schedule of Capital Units [Table Text Block]

As of December 31, 2013 and 2012, the Parent Company, as general partner, owned the following Partnership Units outstanding (in thousands):

	2013	2012
Partnership units owned by the general partner	92,333	90,394
Total partnership units outstanding	92,499	90,572
Percentage of partnership units owned by the general partner	99.8%	99.8%

Preferred Stock

	Preferred Stock Outstanding as of December 31, 2013 and 2012
	Date of Issuance	Shares Issued and Outstanding	Liquidation Preference		Distribution Rate	Callable By Company
Series 6	2/16/2012	10,000,000	$	250,000,000	6.625%	2/16/2017
Series 7	8/23/2012	3,000,000	75,000,000		6.000%	8/23/2017
		13,000,000	$	325,000,000

Schedule of Accumulated Other Comprehensive Income (Loss)

The following table presents changes in the balances of each component of accumulated other comprehensive loss for the year ended December 31, 2013 (in thousands):

		Loss on Settlement of Derivative Instruments		Fair Value of Derivative Instruments		Accumulated Other Comprehensive Income (Loss)
Beginning balance as of December 31, 2012	$	(61,991	)	4,276		(57,715	)
Net gain on cash flow derivative instruments		—		30,878		30,878
Amounts reclassified from accumulated other comprehensive income		9,449		(16	)	9,433
Current period other comprehensive income, net		9,449		30,862		40,311
Ending balance as of December 31, 2013	$	(52,542	)	35,138		(17,404	)