Stock Transactions and Unit Redemptions - Unit Redemption and Share Repurchase Activity (Parenthetical) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Class of Stock [Line Items]
Average price for redemption of limited partnership units	$ 5.03	$ 5.13
Repurchase of Class A common stock, shares	3,046,857
Aggregate purchase price of Class A common stock	$ 15,528	$ 337	$ 392
Average price of Class A common stock	$ 5.09
Class A Common Stock [Member]
Class of Stock [Line Items]
Average price for redemption of FPUs	$ 4.48	$ 6.46
Repurchase of Class A common stock, shares	3,046,857	44,013	60,929
Aggregate purchase price of Class A common stock	$ 15,500	$ 337
Average price of Class A common stock	$ 5.09	$ 7.66	$ 6.43
Limited Partnership [Member]
Class of Stock [Line Items]
Redeemed limited partnership units	10,400,000	14,900,000
Other Ownership Interest [Member]
Class of Stock [Line Items]
Redeemed limited partnership units	1,400,000	1,400,000