Stockholders' Equity - Cash Dividends Declared to Stockholders (Detail) (USD $)	3 Months Ended								39 Months Ended	0 Months Ended	3 Months Ended																12 Months Ended			36 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Dec. 31, 2013	Apr. 26, 2013 Accrued Dividend [Member] Common Stockholders [Member]	Dec. 31, 2013 Accrued Dividend [Member] Common Stockholders [Member]	Sep. 30, 2013 Accrued Dividend [Member] Common Stockholders [Member]	Jun. 30, 2013 Accrued Dividend [Member] Common Stockholders [Member]	Mar. 31, 2013 Accrued Dividend [Member] Common Stockholders [Member]	Dec. 31, 2012 Accrued Dividend [Member] Common Stockholders [Member]	Sep. 30, 2012 Accrued Dividend [Member] Common Stockholders [Member]	Jun. 30, 2012 Accrued Dividend [Member] Common Stockholders [Member]	Mar. 31, 2012 Accrued Dividend [Member] Common Stockholders [Member]	Dec. 31, 2011 Accrued Dividend [Member] Common Stockholders [Member]	Sep. 30, 2011 Accrued Dividend [Member] Common Stockholders [Member]	Jun. 30, 2011 Accrued Dividend [Member] Common Stockholders [Member]	Mar. 31, 2011 Accrued Dividend [Member] Common Stockholders [Member]	Dec. 31, 2010 Accrued Dividend [Member] Common Stockholders [Member]	Sep. 30, 2010 Accrued Dividend [Member] Common Stockholders [Member]	Jun. 30, 2010 Accrued Dividend [Member] Common Stockholders [Member]	Mar. 31, 2010 Accrued Dividend [Member] Common Stockholders [Member]	Dec. 31, 2013 Accrued Dividend [Member] Common Stockholders [Member]	Dec. 31, 2012 Accrued Dividend [Member] Common Stockholders [Member]	Dec. 31, 2011 Accrued Dividend [Member] Common Stockholders [Member]	Dec. 31, 2013 Accrued Dividend [Member] Common Stockholders [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend Declaration Date															Nov. 01, 2012	Jul. 30, 2012	May 03, 2012	Feb. 22, 2012	Oct. 26, 2011	Jul. 27, 2011	May 04, 2011	Feb. 23, 2011	Nov. 03, 2010	Jul. 28, 2010	May 05, 2010	Feb. 24, 2010
Dividend Record Date															Nov. 16, 2012	Aug. 17, 2012	May 18, 2012	Mar. 16, 2012	Nov. 18, 2011	Aug. 19, 2011	May 20, 2011	Mar. 17, 2011	Nov. 18, 2010	Aug. 19, 2010	May 20, 2010	Mar. 17, 2010
Dividend Payment Date															2012-12-07	2012-09-09	2012-06-24	2012-03-20	2011-12-09	2011-09-09	2011-06-24	2011-03-31	2010-12-10	2010-09-10	2010-06-25	2010-03-31
Per Share Amount											$ 0.125	$ 0.125	$ 0.125	$ 0.125	$ 0.125	$ 0.125	$ 0.250	$ 0.250	$ 0.250	$ 0.250	$ 0.250	$ 0.250					$ 0.5	$ 0.75	$ 1	$ 2.25
Total Payment	$ 2,211	$ 2,042	$ 2,356	$ 2,839	$ 3,482	$ 3,439	$ 3,627	$ 2,955	$ 22,951	$ 1,513,000																	$ 12,312,000	$ 16,512,000	$ 22,121,000	$ 50,945,000