Stockholder's Equity - Cash Dividends (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Dividend Payment By Record Date [Line Items]
Per Share Amount	$ 0.09	$ 0.09	$ 0.27	$ 0.27
Total Dividend Paid			$ 17,173	$ 17,395
Record Date Second February Two Thousand Twelve [Member]
Dividend Payment By Record Date [Line Items]
Record Date			Feb. 02, 2012
Payment Date			Feb. 16, 2012
Per Share Amount			$ 0.09
Total Dividend Paid			5,739
Record Date Twenty Six April Two Thousand Twelve [Member]
Dividend Payment By Record Date [Line Items]
Record Date			Apr. 26, 2012
Payment Date			May 10, 2012
Per Share Amount			$ 0.09
Total Dividend Paid			5,737
Record Date Twenty Six July Two Thousand Twelve Member
Dividend Payment By Record Date [Line Items]
Record Date			Jul. 26, 2012
Payment Date			Aug. 09, 2012
Per Share Amount			$ 0.09
Total Dividend Paid			$ 5,697