Federal Home Loan Bank Advances (Summary Of Advances Payable To The Federal Home Loan Bank) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Unamortized premiums	$ 61	$ 85
Federal Home Loan Bank of Boston [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Total Outstanding	2,052,360	1,827,527
Weighted Average Contractual Coupon Rate	0.54%	0.59%
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	2,052,421	1,827,612
Federal Home Loan Bank Advances Maturities Summary Within One Year [Member] | Federal Home Loan Bank of Boston [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Total Outstanding	1,550,000	1,425,000
Weighted Average Contractual Coupon Rate	0.25%	0.34%
FederalHomeLoanBankAdvancesMaturitiesSummaryWithinThree Year [Member] | Federal Home Loan Bank of Boston [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Total Outstanding	145,934
Weighted Average Contractual Coupon Rate	1.80%
FederalHomeLoanBankAdvancesMaturitiesSummaryWithinFourYear [Member] | Federal Home Loan Bank of Boston [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Total Outstanding	500	145,934
Weighted Average Contractual Coupon Rate	5.66%	1.80%
Federal Home Loan Bank Advances Maturities Summary Within Five Year [Member] | Federal Home Loan Bank of Boston [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Total Outstanding		500
Weighted Average Contractual Coupon Rate		5.66%
Federal Home Loan Bank Advances Maturities Summary After Five Year [Member] | Federal Home Loan Bank of Boston [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Total Outstanding	$ 355,926	$ 256,093
Weighted Average Contractual Coupon Rate	1.31%	1.29%