Note Borrowings (Notes payable) (Parenthetical) (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Advances due 2018 To 2029 with fixed Rates 0.89% to 4.19%
Debt Instrument [Line Items]
Advances with the FHLB, earliest maturity	2018
Advances with the FHLB, latest maturity	2029
Advances due 2018 To 2029 with fixed Rates 0.89% to 4.19% | Maximum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	4.19%
Advances due 2018 To 2029 with fixed Rates 0.89% to 4.19% | Minimum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	0.89%
Floating Rate from 0.22% to 0.34% over the 1 month LIBOR with maturities ranging from 2018 to 2019
Debt Instrument [Line Items]
Advances with the FHLB, earliest maturity	2018
Advances with the FHLB, latest maturity	2019
Floating Rate from 0.22% to 0.34% over the 1 month LIBOR with maturities ranging from 2018 to 2019 | Maximum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	0.34%
Floating Rate from 0.22% to 0.34% over the 1 month LIBOR with maturities ranging from 2018 to 2019 | Minimum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	0.22%
Floating Rate from 0.12% to 0.24% over the 3 month LIBOR with maturities ranging from 2018 to 2019)
Debt Instrument [Line Items]
Advances with the FHLB, earliest maturity	2018
Advances with the FHLB, latest maturity	2019
Floating Rate from 0.12% to 0.24% over the 3 month LIBOR with maturities ranging from 2018 to 2019) | Maximum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	0.24%
Floating Rate from 0.12% to 0.24% over the 3 month LIBOR with maturities ranging from 2018 to 2019) | Minimum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	0.12%
Fixed Rate 7.00% Percent Notes Due July 2019 paying interest semiannually, net of debt issuance costs of $2,085
Debt Instrument [Line Items]
Interest Rate Percentage	7.00%
Senior Debt Maturity Year	2019
Debt issuance costs line of credit arrangements net	$ 2,085
Fixed Rate 6.125% to 8.327% Junior Subordinated Deferrable Interest Debentures Due 2027 to 2034, net of debt issuance costs of $436
Debt Instrument [Line Items]
Notes Payable Maturity Year Range Start	2027
Notes Payable Maturity Year Range End	2034
Debt issuance costs line of credit arrangements net	$ 436
Fixed Rate 6.125% to 8.327% Junior Subordinated Deferrable Interest Debentures Due 2027 to 2034, net of debt issuance costs of $436 | Maximum
Debt Instrument [Line Items]
Interest Rate Percentage	8.327%
Fixed Rate 6.125% to 8.327% Junior Subordinated Deferrable Interest Debentures Due 2027 to 2034, net of debt issuance costs of $436 | Minimum
Debt Instrument [Line Items]
Interest Rate Percentage	6.125%