Loans Receivable, Net - Recorded Investment in Residential and Consumer Loans Based on Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Non-performing	$ 18,307	$ 45,360	$ 43,374
Total loans	1,718,687	1,571,579
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Non-performing	1,877	4,328
Total loans	199,349	200,683
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	785,441	781,406
Residential Real Estate [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing	734,774	722,371
Non-performing	3,115	28,213
Total loans	737,889	750,584
Residential Real Estate [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing	47,552	30,821
Total loans	47,552	30,821
Residential Real Estate [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing	197,472	196,355
Non-performing	1,877	4,328
Total loans	$ 199,349	$ 200,683