CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities:
Net income	$ 91,230	$ 91,353	$ 78,829
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	13,132	13,082	12,236
Amortization of intangible assets	3,663	4,287	4,469
Net (accretion) amortization on securities, loans and borrowings	(3,289)	(3,533)	(5,959)
Stock-based compensation	4,201	3,993	3,961
Provision for loan losses	6,447	7,178	7,992
Provision for deferred income taxes	10,716	7,461	7,130
Amortization of mortgage servicing rights	409	444	529
Income from bank-owned life insurance policies	(1,086)	(1,037)	(1,066)
Loss/(gain) on sales of investment securities, net	4	0	(80,768)
Loss on debt extinguishments	0	0	87,336
Net (gain) loss on sale of loans and other assets	(180)	(154)	257
Change in other assets and liabilities	(8,784)	127	(11,762)
Net cash provided by operating activities	116,463	123,201	103,184
Investing activities:
Proceeds from sales of available-for-sale investment securities	221,136	0	713,694
Proceeds from sales of held-to-maturity investment securities	0	0	450,032
Proceeds from maturities of available-for-sale investment securities	169,562	137,282	234,021
Proceeds from maturities of held-to-maturity investment securities	0	0	31,595
Proceeds from maturities of other securities	1,790	13	26,649
Purchases of available-for-sale investment securities	(503,000)	(310,517)	(923,588)
Purchases of held-to-maturity investment securities	0	0	(8,308)
Purchases of other securities	0	(7,500)	0
Net change in loans	(176,754)	(137,207)	(248,962)
Cash received for acquisitions, net of cash acquired of $81,772, $0, and $0, respectively	25,505	(924)	291,980
Purchases of premises and equipment, net	(12,400)	(13,376)	(13,855)
Net cash (used in)/provided by investing activities	(274,161)	(332,229)	553,258
Financing activities:
Net change in deposits	238,969	39,220	(35,451)
Net change in borrowings, net of payments of $0, $13 and $815,384	(36,700)	196,087	(673,484)
Issuance of common stock	9,774	9,417	15,239
Purchases of treasury stock	(9,126)	(4,368)	0
Sales of treasury stock	16,571	1,531	0
Cash dividends paid	(49,273)	(46,178)	(43,482)
Tax benefits from share-based payment arrangements	2,297	2,068	1,825
Net cash provided by/(used in) financing activities	172,512	197,777	(735,353)
Change in cash and cash equivalents	14,814	(11,251)	(78,911)
Cash and cash equivalents at beginning of year	138,396	149,647	228,558
Cash and cash equivalents at end of year	153,210	138,396	149,647
Supplemental disclosures of cash flow information:
Cash paid for interest	11,252	11,937	30,141
Cash paid for income taxes	28,891	29,457	23,648
Supplemental disclosures of noncash financing and investing activities:
Dividends declared and unpaid	13,605	12,254	11,332
Transfers from loans to other real estate	3,943	2,546	8,325
Transfer of investment securities from held-to-maturity to available-for-sale	0	0	198,890
Acquisitions:
Common stock issued	102,201	0	0
Fair value of assets acquired, excluding acquired cash and intangibles	675,948	64	3,678
Fair value of liabilities assumed	$ 699,894	$ 0	$ 303,494