Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows From Operating Activities:
Net Income	$ 132,217	$ 142,943	$ 152,276
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	45,571	13,091	8,660
Provision for unfunded commitments	1,380	0	0
Depreciation and amortization	4,696	6,174	6,969
Gains on sale of loans	(22,089)	(8,474)	(5,963)
Gain on MSRs	(667)	0	0
Securities premium amortization (discount accretion), net	8,196	5,186	4,445
Origination of loans held for sale	(1,240,682)	(665,726)	(325,109)
Proceeds from sale of loans held for sale	1,231,273	636,747	337,256
Net increase in cash surrender value of BOLI	(2,071)	(1,703)	(1,507)
Deferred income tax (benefit) expense	(8,332)	(61)	(3,497)
Net gain on sale of other real estate owned	(1,180)	0	0
Net gain on sale of investment securities	(1,815)	(1,517)	(97)
Stock-based compensation expense	5,324	7,684	6,494
Net tax (expense) benefits from stock compensation	118	(48)	110
Increase in other assets	(28,626)	(21,421)	(16,643)
Increase in other liabilities	9,826	19,809	2,061
Net cash provided by operating activities	133,139	132,684	165,455
Cash Flows From Investing Activities:
Purchases of available-for-sale investment securities	(739,955)	(374,648)	(331,884)
Proceeds from maturities of available-for-sale securities	302,471	214,204	93,848
Proceeds from sale/call of available-for-sale securities	124,144	104,785	36,292
Purchases of Federal Reserve and Federal Home Loan Bank stock	(9,160)	(100,939)	(47,872)
Proceeds from redemption of Federal Reserve and Federal Home Loan Bank stock	4,250	89,250	60,690
Net increase in loans	(240,911)	(563,771)	(583,393)
Purchase of BOLI	0	(580)	(11,000)
Purchase of annuities	0	(2,589)	0
Proceeds from sale of other real estate owned	4,430	0	0
Purchases of premises and equipment	(2,945)	(2,839)	(1,482)
Net cash used in investing activities	(557,676)	(637,127)	(784,801)
Cash Flows From Financing Activities:
Increase in deposits	1,964,812	250,106	1,120,301
Increase (decrease) in customer repurchase agreements	(4,254)	567	(46,148)
Increase (decrease) in short-term borrowings	50,000	250,000	(325,000)
Increase in long-term borrowings	50,000	0	0
Proceeds from exercise of equity compensation plans	63	332	776
Proceeds from employee stock purchase plan	760	782	808
Common stock repurchased	(61,432)	(54,903)	0
Cash dividends paid	(28,330)	(22,332)	0
Net cash provided by financing activities	1,971,619	424,552	750,737
Net (Decrease) Increase In Cash and Cash Equivalents	1,547,082	(79,891)	131,391
Cash and Cash Equivalents at Beginning of Period	241,973	321,864	190,473
Cash and Cash Equivalents at End of Period	1,789,055	241,973	321,864
Supplemental Cash Flows Information:
Interest paid	70,183	105,985	73,806
Income taxes paid	37,400	54,650	55,200
Non-Cash Investing Activities
Initial recognition of operating lease right-of-use assets	1,696	29,574	0
Transfers from loans to other real estate owned	6,750	93	0
Change in fair value of cash flow hedge	(904)	0	0
Change in fair value of investments	$ 17,822	$ 0	$ 0