Discontinued Operations - Discontinued Operations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Discontinued Operations And Disposal Groups [Abstract]
Revenues									$ 988	$ 3,470	$ 14,531
Gain on sale									7,659	16,369	5,431
Income from discontinued operations	$ 4,588	$ 312	$ 2,374	$ 640	$ 5,339	$ 8,914	$ 642	$ 2,312	$ 7,914	$ 17,207	$ 14,594
Income from discontinued operations - diluted per share/unit									$ 0.05	$ 0.13	$ 0.13