MAALP Capital (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Limited Partners' Capital Account [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance	$ 161,310	$ 166,746
Net Income Allocated to Limited Partners	10,984	2,621
General partner units issued in exchange for limited partner units	(184)	(799)
Adjustment for noncontrolling interest ownership in operating partnership	(45)	(79)
Distributions	(6,449)	(6,143)
Ending Balance	165,616	162,346
General Partners' Capital Account [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance	2,890,858	2,946,598
Net Income Allocated to General Partners	197,566	46,479
Issuance of units	184	575
Units repurchased and retired	(945)	(336)
Exercise of unit options	420	9,544
General partner units issued in exchange for limited partner units	184	799
Units issued in exchange for redeemable units		998
Redeemable stock fair market value	173	(848)
Adjustment for noncontrolling interest ownership in operating partnership	45	79
Amortization of unearned compensation	3,167	2,045
Distributions	(116,066)	(109,680)
Ending Balance	2,975,586	2,896,253
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance	(376)	174
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)	1,440	(1,590)
Ending Balance	1,064	(1,416)
Total Partnership Capital [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance	3,051,792	3,113,518
Net Income Available for Common Unitholders	208,550	49,100
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)	1,440	(1,590)
Issuance of units	184	575
Units repurchased and retired	(945)	(336)
Exercise of unit options	420	9,544
General partner units issued in exchange for limited partner units	0	0
Units issued in exchange for redeemable units		998
Redeemable stock fair market value	173	(848)
Adjustment for noncontrolling interest ownership in operating partnership	0	0
Amortization of unearned compensation	3,167	2,045
Distributions	(122,515)	(115,823)
Ending Balance	$ 3,142,266	$ 3,057,183