Condensed Parent Company Financial Statements - Summary of Balance Sheet of Parent Company (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
ASSETS
Cash	$ 183,921	$ 203,364
Securities	469,833	552,949
Goodwill	54,042	54,042	$ 44,962
Total assets	7,018,952	6,692,829	6,574,972
LIABILITIES AND STOCKHOLDERS' EQUITY
Other liabilities	27,342	31,502
Junior subordinated debentures	31,959	31,959
Stockholders’ equity	711,094	655,510	$ 609,314
Total liabilities and stockholders' equity	7,018,952	6,692,829
Parent Company [Member]
ASSETS
Cash	57,537	45,437
Securities	97	103
Investments in subsidiaries	681,861	639,119
Goodwill	450	450
Dividends receivable	6,998	6,773
Other assets	2,610	1,688
Total assets	749,553	693,570
LIABILITIES AND STOCKHOLDERS' EQUITY
Other liabilities	6,500	6,101
Junior subordinated debentures	31,959	31,959
Stockholders’ equity	711,094	655,510
Total liabilities and stockholders' equity	$ 749,553	$ 693,570