Note Loans (Composition of loans held-in-portfolio-covered loans and past due status) (Detail) - USD ($) $ in Thousands	Sep. 30, 2017		Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans covered under loss-sharing agreements with the FDIC	$ 524,854		$ 572,878
Covered loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	127,752		110,336
Current	397,102		462,542
Loans covered under loss-sharing agreements with the FDIC	524,854	[1]	572,878	[2]
Covered loans | Past Due 30 To 59 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	49,229		26,257
Covered loans | Past Due 60 To 89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	16,546		13,149
Covered loans | Past Due 90 Days or More
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	61,977		70,930
Covered loans | Mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	124,803		108,266
Current	385,408		448,304
Loans covered under loss-sharing agreements with the FDIC	510,211		556,570
Covered loans | Mortgages | Past Due 30 To 59 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	47,726		25,506
Covered loans | Mortgages | Past Due 60 To 89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	16,104		12,904
Covered loans | Mortgages | Past Due 90 Days or More
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	60,973		69,856
Covered loans | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,949		2,070
Current	11,694		14,238
Loans covered under loss-sharing agreements with the FDIC	14,643		16,308
Covered loans | Consumer | Past Due 30 To 59 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,503		751
Covered loans | Consumer | Past Due 60 To 89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	442		245
Covered loans | Consumer | Past Due 90 Days or More
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	$ 1,004		$ 1,074

[1] Includes $296 million pledged to secure credit facilities at the FHLB which are not permitted to sell or repledge the collateral.

[2] Includes $337 million pledged to secure credit facilities at the FHLB which are not permitted to sell or repledge the collateral.