Parent Company Condensed Financial Information - Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Information [Line Items]
Cash	$ 99,399	$ 109,580	$ 108,356	$ 337,711
Other assets	102,583	97,024
Total Assets	6,318,354	4,964,686
Other liabilities	68,758	61,789
Total Liabilities	5,526,117	4,356,297
Total Shareholders' Equity	792,237	608,389	571,306	537,422
Total Liabilities and Shareholders’ Equity	6,318,354	4,964,686
Parent Company
Condensed Financial Information [Line Items]
Cash	12,595	38,028	$ 14,852	$ 12,202
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	777,795	565,927
Nonbank subsidiaries	20,624	20,569
Other assets	2,530	5,567
Total Assets	813,544	630,091
Long-term debt	20,619	20,619
Other liabilities	688	1,083
Total Liabilities	21,307	21,702
Total Shareholders' Equity	792,237	608,389
Total Liabilities and Shareholders’ Equity	$ 813,544	$ 630,091