Federal Home Loan Bank Advances - Maturities of FHLB Advances Outstanding (Parenthetical) (Detail)	Dec. 31, 2012 Maturities January 2014 with fixed rate 3.55% [Member]	Dec. 31, 2012 Maturities January 2015 with fixed rate 0.80% [Member]	Dec. 31, 2012 Maturity December 2016 with fixed rate 0.79% [Member]	Dec. 31, 2012 Maturity June 2018 fixed rate 1.24% [Member]	Dec. 31, 2011 Maturity January 2012, fixed rate 2.37% [Member]	Dec. 31, 2012 Minimum [Member] Maturity June 2017 through December 2017, with fixed rates ranging from 0.89% to 0.99% [Member]	Dec. 31, 2011 Minimum [Member] Maturities January 2014 through August 2014, with fixed rates ranging from 2.06% to 3.55% [Member]	Dec. 31, 2011 Minimum [Member] Maturities January 2015 fixed rate 2.00% and July 2015 fixed rate 4.76% [Member]	Dec. 31, 2012 Maximum [Member] Maturity June 2017 through December 2017, with fixed rates ranging from 0.89% to 0.99% [Member]	Dec. 31, 2011 Maximum [Member] Maturities January 2014 through August 2014, with fixed rates ranging from 2.06% to 3.55% [Member]	Dec. 31, 2011 Maximum [Member] Maturities January 2015 fixed rate 2.00% and July 2015 fixed rate 4.76% [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Interest rates on Federal Home Loan Bank Advances	3.55%	0.80%	0.79%	1.24%	2.37%	0.89%	2.06%	2.00%	0.99%	3.55%	4.76%