Noncontrolling Interests (Redeemable Preferred Units) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Beginning balance			$ 55,652	$ 55,652
Issuance of redeemable preferred units (Series Four Preferred Units)			79,405
Net income	874	832	2,440	2,497
Distributions			(2,440)	(2,497)
Redemption of redeemable preferred units (Series Four Preferred Units)			(18,329)
Conversion of redeemable preferred units (Series Two Preferred Units) to common units			(5,852)
Ending balance	$ 110,876	$ 55,652	$ 110,876	$ 55,652