Condensed Consolidated Statements of Changes in Equity (USD $) In Thousands, unless otherwise specified	Total	Common Units	Class B Units	Non-controlling Interest	Redeemable Non-Controlling Interest (Temporary Equity)
Balance at Dec. 31, 2012	$ 3,111,398	$ 2,097,404	$ 752,531	$ 261,463
Balance (in units) at Dec. 31, 2012		127,494	19,954
Increase (Decrease) in Equity
Issuance of units in public offerings, net of offering costs	103,937	103,937
Issuance of units in public offerings, net of offering costs (in units)		1,921
Distributions paid	(106,026)	(105,945)		(81)
Contributions from non-controlling interest	385,219			385,219
Redeemable non-controlling interest classified as temporary equity	(326,249)			(326,249)	326,249
Share-based compensation activity	(1,204)	(1,204)
Share-based compensation activity (in units)		161
Excess tax benefits related to share-based compensation	651	651
Deferred income tax impact from changes in equity	(10,235)	(10,235)
Net income (loss)	(21,131)	(15,458)		(5,673)
Balance at Mar. 31, 2013	3,136,360	2,069,150	752,531	314,679	326,249
Balance (in units) at Mar. 31, 2013		129,576	19,954
Balance at Dec. 31, 2013	235,617
Balance at Dec. 31, 2013	4,798,133	3,476,295	602,025	719,813	235,617
Balance (in units) at Dec. 31, 2013		157,766	15,964
Increase (Decrease) in Equity
Issuance of units in public offerings, net of offering costs	271,880	271,880
Issuance of units in public offerings, net of offering costs (in units)		4,249
Distributions paid	(136,495)	(136,405)		(90)
Redeemable non-controlling interest classified as temporary equity	104,052			104,052	(104,052)
Share-based compensation activity	(2,881)	(2,881)
Share-based compensation activity (in units)		210
Deferred income tax impact from changes in equity	(7,874)	(7,874)
Net income (loss)	15,916	12,492		3,424
Balance at Mar. 31, 2014	131,565
Balance at Mar. 31, 2014	$ 5,042,731	$ 3,613,507	$ 602,025	$ 827,199	$ 131,565
Balance (in units) at Mar. 31, 2014		162,225	15,964