Segment Information, Nature of Operations, and Certain Concentrations - Interest Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Other Significant Reconciling Item [Line Items]
Consolidated interest income	$ 8,680	$ 7,696	$ 6,251
Mortgage Banking [Member]
Segment Reporting Other Significant Reconciling Item [Line Items]
Interest income	7,569	6,485	4,940
Operating Segments [Member]
Segment Reporting Other Significant Reconciling Item [Line Items]
Interest income	7,569	6,485	4,940
Consolidation adjustments and other [Member]
Segment Reporting Other Significant Reconciling Item [Line Items]
Other unallocated interest income	$ 1,111	$ 1,211	$ 1,311