Cash Dividends Declared (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012
Dividend Payment 1st
Dividend Declared [Line Items]
Dividend per share	$ 0.025
Date declared	Mar. 04, 2011
Date of record	May 02, 2011
Payment date	May 16, 2011
Dividend Payment 2nd
Dividend Declared [Line Items]
Dividend per share	$ 0.025
Date declared	Jun. 27, 2011
Date of record	Aug. 02, 2011
Payment date	Aug. 16, 2011
Dividend Payment 3rd
Dividend Declared [Line Items]
Dividend per share	$ 0.025
Date declared	Nov. 04, 2011
Date of record	Nov. 18, 2011
Payment date	Nov. 29, 2011
Dividend Payment 4th
Dividend Declared [Line Items]
Dividend per share	$ 0.025
Date declared	Jan. 11, 2012
Date of record	Feb. 01, 2012
Payment date	Feb. 15, 2012
Dividend Payment 5th
Dividend Declared [Line Items]
Dividend per share	$ 0.025
Date declared	Mar. 06, 2012
Date of record	May 01, 2012
Payment date	May 15, 2012
Dividend Payment 6th
Dividend Declared [Line Items]
Dividend per share	$ 0.025
Date declared	Jun. 13, 2012
Date of record	Aug. 01, 2012
Payment date	Aug. 15, 2012
Dividend Payment 7th
Dividend Declared [Line Items]
Dividend per share	$ 0.025
Date declared	Jul. 31, 2012
Date of record	Nov. 01, 2012
Payment date	Nov. 15, 2012
Dividend Payment 8th
Dividend Declared [Line Items]
Dividend per share	$ 0.025
Date declared	Nov. 02, 2012
Date of record	Feb. 01, 2013
Payment date	Feb. 15, 2013