Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Operating activities
Net income	$ 2,008,000	$ 45,110,000
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Provision for credit losses on loans	26,350,000	1,500,000
Depreciation, amortization and accretion	4,937,000	409,000
Deferred income tax (benefit) expense	(2,791,000)	5,949,000
Funding of mortgage loans held for sale	(715,760,000)	(384,103,000)
Proceeds from sales of mortgage loans held for sale	607,017,000	416,032,000
Gains on sales of mortgage loans held for sale	(21,782,000)	(7,888,000)
Valuation adjustment to mortgage servicing rights	9,571,000	0	$ 1,836,000
Gains on sales of securities	0	(13,000)
Gains on sales of premises and equipment	0	(89,000)
Stock-based compensation expense	2,750,000	2,637,000
Net change in other loans held for sale	0	70,375,000
(Decrease) increase in other assets	(70,631,000)	5,982,000
Increase (decrease) in other liabilities	35,331,000	(15,794,000)
Net cash (used in) provided by operating activities	(123,000,000)	140,107,000
Investing activities
Purchases of securities available for sale	(123,670,000)	(49,577,000)
Proceeds from sales of securities available for sale	0	10,611,000
Proceeds from call/maturities of securities available for sale	76,269,000	48,509,000
Net increase in loans	(69,337,000)	(808,000)
Purchases of premises and equipment	(1,941,000)	(7,242,000)
Proceeds from sales of premises and equipment	0	135,000
Net change in FHLB stock	(12,432,000)	10,441,000
Proceeds from sales of other assets	770,000	12,965,000
Other, net	0	(104,000)
Net cash (used in) provided by investing activities	(130,341,000)	24,930,000
Financing activities
Net increase in noninterest-bearing deposits	90,289,000	47,517,000
Net increase in interest-bearing deposits	109,115,000	93,175,000
Net increase (decrease) in short-term borrowings	313,946,000	(300,116,000)
Repayment of long-term debt	(43,000)	(216,000)
Cash paid for dividends	(12,555,000)	(12,442,000)
Repurchase of shares in connection with stock repurchase program	(24,569,000)	0
Net cash provided by (used in) financing activities	476,183,000	(172,082,000)
Net increase (decrease) in cash and cash equivalents	222,842,000	(7,045,000)
Cash and cash equivalents at beginning of period	414,930,000	569,111,000	569,111,000
Cash and cash equivalents at end of period	637,772,000	562,066,000	$ 414,930,000
Supplemental disclosures
Cash paid for interest	26,264,000	23,887,000
Cash paid for income taxes	4,176,000	5,325,000
Noncash transactions:
Transfers of loans to other real estate owned	1,641,000	885,000
Financed sales of other real estate owned	159,000	120,000
Recognition of operating right-of-use assets	1,968,000	54,338,000
Recognition of operating lease liabilities	$ 2,034,000	$ 57,857,000