Derivatives - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended			2 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 06, 2014	Jan. 29, 2014	Aug. 01, 2014	Oct. 31, 2008
Derivative [Line Items]
Mark-to-Market Gain on Interest Rate Protection Agreements	$ 0	$ 52	$ (328)
Settlement payments of mark-to-market gains or losses		774
Series F Preferred Stock
Derivative [Line Items]
Minimum fixed coupon rate of preferred stock	2.375%
Number of years of U.S. treasury rate one				30 years
Number of years of U.S. treasury rate two				10 years
LIBOR rate				3-month LIBOR
New coupon rate of preferred stock	6.236%			6.275%
Group I Swaps
Derivative [Line Items]
Swaps, Number of Instruments Held					4
Swaps, Notional Amount					200,000
Swaps, Average Fixed Interest Rate					2.29%
Group II Swaps
Derivative [Line Items]
Swaps, Number of Instruments Held						3
Swaps, Notional Amount						220,000
Swaps, Average Fixed Interest Rate						2.5795%
Series F Agreement
Derivative [Line Items]
Swaps, Notional Amount	$ 200,000						$ 50,000
Swaps, Average Fixed Interest Rate							5.2175%