CONSOLIDATED STATEMENTS OF INCOME (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Interest income:
Interest and fees on loans	$ 45,591	$ 45,693
Interest and dividends on taxable investments	12,060	12,470
Interest and dividends on nontaxable investments	4,803	5,076
Total interest income	62,454	63,239
Interest expense:
Interest on deposits	1,800	2,235
Interest on borrowings	200	284
Interest on subordinated debt held by unconsolidated subsidiary trusts	614	612
Total interest expense	2,614	3,131
Net interest income	59,840	60,108
Provision for loan losses	623	1,000
Net interest income after provision for loan losses	59,217	59,108
Noninterest income:
Deposit service fees	12,470	12,255
Other banking services	1,055	1,190
Employee benefit services	11,075	10,435
Wealth management services	4,446	4,474
Total noninterest income	29,046	28,354
Noninterest expenses:
Salaries and employee benefits	31,029	30,740
Occupancy and equipment	7,395	7,691
Data processing and communications	6,990	6,803
Amortization of intangible assets	919	1,141
Legal and professional fees	1,746	1,947
Office supplies and postage	1,580	1,551
Business development and marketing	1,564	1,730
FDIC insurance premiums	989	1,019
Acquisition expenses	395	123
Other	3,341	3,176
Total noninterest expenses	55,948	55,921
Income before income taxes	32,315	31,541
Income taxes	10,018	9,368
Net income	$ 22,297	$ 22,173
Basic earnings per share (in dollars per share)	$ 0.55	$ 0.55
Diluted earnings per share (in dollars per share)	$ 0.54	$ 0.54
Cash dividends declared per share (in dollars per share)	$ 0.30	$ 0.28