Loans Receivable and Allowance for Loan Losses - Summary of Recorded Investment Net Charge-Offs, Unpaid Principal Balance and Related Allowance for Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, Total	$ 30,503		$ 40,325
Unpaid Principal Balance, Total	33,381		44,234
Related Allowance	3,369		1,342
Average Recorded Investment, Total	35,418	39,755
Interest Income Recognized, Total	361	412
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, With no related allowance recorded	6,922		13,825
Recorded Investment Net of Charge Offs, With an allowance recorded	6,478		1,833
Unpaid Principal Balance, With no related allowance recorded	8,376		15,348
Unpaid Principal Balance, With an allowance recorded	6,488		1,833
Related Allowance	2,295		818
Average Recorded Investment, With no related allowance recorded	10,374	12,003
Average Recorded Investment, With an allowance recorded	4,156	1,653
Interest Income Recognized, With an allowance recorded	5	8
Interest Income Recognized, With no related allowance recorded	164	99
Commercial real estate
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, With no related allowance recorded	11,496		18,977
Recorded Investment Net of Charge Offs, With an allowance recorded	1,409		1,410
Unpaid Principal Balance, With no related allowance recorded	11,641		19,121
Unpaid Principal Balance, With an allowance recorded	1,409		1,410
Related Allowance	864		304
Average Recorded Investment, With no related allowance recorded	15,237	17,139
Average Recorded Investment, With an allowance recorded	1,410	2,350
Interest Income Recognized, With an allowance recorded	0	1
Interest Income Recognized, With no related allowance recorded	191	274
Construction
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, With no related allowance recorded	2,325		2,325
Recorded Investment Net of Charge Offs, With an allowance recorded	0		0
Unpaid Principal Balance, With no related allowance recorded	3,594		2,325
Unpaid Principal Balance, With an allowance recorded	0		0
Related Allowance	0		0
Average Recorded Investment, With no related allowance recorded	2,325	2,551
Average Recorded Investment, With an allowance recorded	0	1,350
Interest Income Recognized, With an allowance recorded	0	15
Interest Income Recognized, With no related allowance recorded	0	0
Other
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, With no related allowance recorded	20		21
Recorded Investment Net of Charge Offs, With an allowance recorded	53		114
Unpaid Principal Balance, With no related allowance recorded	20		21
Unpaid Principal Balance, With an allowance recorded	53		114
Related Allowance	25		32
Average Recorded Investment, With no related allowance recorded	21	3
Average Recorded Investment, With an allowance recorded	84	64
Interest Income Recognized, With an allowance recorded	1	1
Interest Income Recognized, With no related allowance recorded	0	0
Residential real estate
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, With no related allowance recorded	1,438		1,455
Recorded Investment Net of Charge Offs, With an allowance recorded	362		365
Unpaid Principal Balance, With no related allowance recorded	1,438		3,697
Unpaid Principal Balance, With an allowance recorded	362		365
Related Allowance	185		188
Average Recorded Investment, With no related allowance recorded	1,447	2,391
Average Recorded Investment, With an allowance recorded	364	251
Interest Income Recognized, With an allowance recorded	0	1
Interest Income Recognized, With no related allowance recorded	$ 0	$ 13