MAALP Capital (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 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	4,881	10,984
General partner units issued in exchange for limited partner units	(158)	(184)
Adjustment for noncontrolling interest ownership in operating partnership	(54)	(45)
Distributions	(6,820)	(6,449)
Ending Balance	163,575	165,616
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	88,557	197,566
Issuance of units	186	184
Units repurchased and retired	(1,742)	(945)
Units Issued During Period, Value, Unit Options Exercised		420
General partner units issued in exchange for limited partner units	158	184
Units issued in exchange for redeemable units	123
Redeemable stock fair market value	(1,518)	173
Adjustment for noncontrolling interest ownership in operating partnership	54	45
Amortization of unearned compensation	4,383	3,167
Distributions	(123,852)	(116,066)
Ending Balance	2,960,045	2,975,586
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)	(2,702)	1,440
Ending Balance	(4,320)	1,064
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	93,438	208,550
Other comprehensive (loss) income - derivatives insturments (cash flow hedges)	(2,702)	1,440
Issuance of units	186	184
Units repurchased and retired	(1,742)	(945)
Units Issued During Period, Value, Unit Options Exercised		420
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	(1,518)	173
Adjustment for noncontrolling interest ownership in operating partnership	0	0
Amortization of unearned compensation	4,383	3,167
Distributions	(130,672)	(122,515)
Ending Balance	$ 3,119,300	$ 3,142,266