Summary of Future Rental Payments Under Capital Ground Lease (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Land
Capital Leased Assets [Line Items]
Option to purchase leased asset, price		$ 5.0
Lease option to purchase month and year	2014-10	2014-10