Income Taxes - Dividends Per Share (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Common Dividends Declared Per Share [Line Items]
Amount Per Share	$ 0.500	$ 0.600	$ 0.640
Dividends paid percentage	100.00%	100.00%	100.00%
Non-qualified dividends [Member]
Common Dividends Declared Per Share [Line Items]
Amount Per Share			$ 0.477
Dividends paid percentage			74.53%
Qualified Dividends [Member]
Common Dividends Declared Per Share [Line Items]
Amount Per Share			$ 0.095
Dividends paid percentage			14.78%
Non-taxable return of capital [Member]
Common Dividends Declared Per Share [Line Items]
Amount Per Share	$ 0.500	$ 0.600	$ 0.068
Dividends paid percentage	100.00%	100.00%	10.69%