Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Assets [Abstract]
Cash and due from banks	$ 201,487	$ 168,119
Interest-bearing bank deposits	41,987	130,577
Cash and cash equivalents	243,474	298,696
Securities available for sale	1,783,208	1,385,650
Loans, net of unearned discounts and deferred fees, including $31,891 and $42,627 of loans covered by a FDIC loss share agreement at September 30, 2019 and September 30, 2018, respectively, and $812,991 and $865,386 of loans at fair value under the fair value option at September 30, 2019 and September 30, 2018, respectively, and $7,351 and $5,456 of loans held for sale at September 30, 2019 and September 30, 2018, respectively	9,706,763	9,415,924
Allowance for loan and lease losses	(70,774)	(64,540)
Net loans	9,635,989	9,351,384
Premises and equipment, including $2,757 and $1,104 of property held for sale at September 30, 2019 and September 30, 2018, respectively	120,645	113,839
Accrued interest receivable	58,699	58,948
Other repossessed property, including $0 and $131 of property covered by a FDIC loss share agreement at September 30, 2019 and September 30, 2018, respectively	36,764	23,074
Goodwill	739,023	739,023
Cash surrender value of life insurance policies	30,796	30,461
Net deferred tax assets	7,286	30,132
Other assets	132,417	85,601
Total assets	12,788,301	12,116,808
Deposits
Noninterest-bearing	1,956,025	1,842,704
Interest-bearing	8,344,314	7,890,795
Total deposits	10,300,339	9,733,499
Securities sold under agreements to repurchase	68,992	90,907
FHLB advances and other borrowings	340,000	275,000
Subordinated debentures and subordinated notes payable	108,636	108,468
Accrued expenses and other liabilities	70,085	68,383
Total liabilities	10,888,052	10,276,257
Stockholders’ equity
Common stock, $0.01 par value, authorized 500,000,000 shares; 56,283,659 shares issued and outstanding at September 30, 2019 and 58,917,147 shares issued and outstanding at September 30, 2018	563	589
Additional paid-in capital	1,228,714	1,318,457
Retained earnings	657,475	553,014
Accumulated other comprehensive income (loss)	13,497	(31,509)
Total stockholders' equity	1,900,249	1,840,551
Total liabilities and stockholders' equity	$ 12,788,301	$ 12,116,808