Determination of Gain Recognized upon Disposition of PVG (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended
	Jun. 30, 2010	Dec. 31, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash proceeds, net of offering costs (8,827,429 units x $15.76 per unit)	$ 139,120	$ 139,120
Carrying value of noncontrolling interests in PVG at date of disposition		382,324
Gains Losses on Sales or Disposition of Assets, Total		521,444
Less: Carrying value of PVG's assets and liabilities at date of disposition		(434,782)
Gain on sale of discontinued operations		86,662
Income tax expense	(35,116)	(35,116)
Gain on sale of discontinued operations, net of tax	$ 51,546	$ 51,546