Supplemental Cash Flow Disclosures - Non-cash Investing and Financing Activities (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Supplemental Cash Flow Information [Abstract]
Unsettled Bank Owned Life Insurance Proceeds	$ 0	$ 523
Cash paid during the period for:
Interest	8,917	9,583
Income Taxes Paid, Net	11,394	10,500
Non-cash investing and financing activities:
Loans Transferred to Other Real Estate Owned and Repossessions	1,519	2,632
Fair value of loans transferred from held to maturity to held for sale	9,053	3,573
Gross increase in market value adjustment to securities available for sale	3,642	13,845
Gross (decrease) increase in market value adjustment to securities derivatives	(508)	2,053
Investments committed to purchase not settled	0	1,946
Stock Issued During Period, Value, Treasury Stock Reissued	2,258	0
Noncash or Part Noncash Acquisition, Value of Assets Acquired	$ 37,087	$ 0