MAALP Capital (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Limited Partners' Capital Account [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance	$ 165,726	$ 161,310
Net Income Allocated to Limited Partners	2,395	3,410
General partner units issued in exchange for limited partner units	(33)	(46)
Adjustment for noncontrolling interest ownership in operating partnership	(172)	(128)
Distributions	(3,412)	(3,226)
Ending Balance	164,504	161,320
General Partners' Capital Account [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance	2,993,696	2,890,858
Net Income Allocated to General Partners	43,413	61,267
Issuance of units	90	8
Units repurchased and retired	(1,730)	(937)
General partner units issued in exchange for limited partner units	33	46
Units issued in exchange for redeemable units	123
Redeemable stock fair market value	(1,100)	(209)
Adjustment for noncontrolling interest ownership in operating partnership	172	128
Amortization of unearned compensation	2,078	1,462
Distributions	(61,928)	(58,034)
Ending Balance	2,974,847	2,894,589
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance	(1,618)	(376)
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)	(2,519)	(2,155)
Ending Balance	(4,137)	(2,531)
Total Partnership Capital [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance	3,157,804	3,051,792
Net Income Available for Common Unitholders	45,808	64,677
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)	(2,519)	(2,155)
Issuance of units	90	8
Units repurchased and retired	(1,730)	(937)
General partner units issued in exchange for limited partner units	0	0
Units issued in exchange for redeemable units	123
Redeemable stock fair market value	(1,100)	(209)
Adjustment for noncontrolling interest ownership in operating partnership	0	0
Amortization of unearned compensation	2,078	1,462
Distributions	(65,340)	(61,260)
Ending Balance	$ 3,135,214	$ 3,053,378