MAALP Capital (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014 Limited Partners' Capital Account [Member]	Sep. 30, 2014 General Partners' Capital Account [Member]	Sep. 30, 2014 Accumulated Other Comprehensive Income (Loss) [Member]	Sep. 30, 2014 Total Partnership Capital [Member]	Sep. 30, 2013 Prior Period Rollforward [Member] Limited Partners' Capital Account [Member]	Sep. 30, 2013 Prior Period Rollforward [Member] General Partners' Capital Account [Member]	Sep. 30, 2013 Prior Period Rollforward [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Sep. 30, 2013 Prior Period Rollforward [Member] Total Partnership Capital [Member]
Capital Disclosure [Line Items]
Beginning Balance	$ 166,746	$ 2,946,598	$ 174	$ 3,113,518	$ 38,154	$ 927,734	$ (26,881)	$ 939,007
Net Income Allocated to Limited Partners	6,364				4,518
Net Income Allocated to General Partners		113,455				112,850
Net Income Available for Common Unitholders				119,819				117,368
Other comprehensive income - derivatives insturments (cash flow hedges)			303	303			22,193	22,193
Issuance of units	0	728		728		25,038		25,038
Units repurchased and retired		(456)		(456)		(682)		(682)
Exercise of unit options		11,916		11,916
General partner units issued in exchange for limited partner units	(992)	992		0	(550)	550		0
Units issued in exchange for redeemable units		998		998
Redeemable stock fair market value		(286)		(286)		209		209
Adjustment for noncontrolling interest ownership in operating partnership	28	(28)		0	1,218	16,597		17,815
Amortization of unearned compensation		3,180		3,180		1,729		1,729
Distributions	(9,209)	(164,598)		(173,807)	(3,557)	(89,109)		(92,666)
Ending Balance	$ 162,937	$ 2,912,499	$ 477	$ 3,075,913	$ 39,783	$ 994,916	$ (4,688)	$ 1,030,011