Recent Accounting and Regulatory Pronouncements - Impact of ASU (Details) - USD ($)		Jan. 01, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Assests:
Securities available for sale, at fair value (Cost of $1,915,461 and allowance for credit losses of $0 for March 31, 2020)			$ 1,971,195,000	$ 1,956,047,000	$ 1,466,249,000
Investment Securities - Held to Maturity			0
Non - Acquired Loans				11,375,104,000	11,146,122,000
Allowance for credit losses			(144,785,000)	(56,927,000)	(56,522,000)	$ (55,798,000)
Deferred tax assets			46,365,000	31,316,000	31,884,000
Accrued Interest Receivable - Loans			30,200,000
Liabilities:
Reserve for Loan Losses - Unfunded Commitments			144,785,000	61,991,000	56,522,000
Equity:
Retained Earnings (Accumulated Deficit)			643,345,000	679,895,000	582,034,000
Credit Discount on Acquired Credit Impaired Loans		$ 3,408,000
Financing Receivable, Allowance for Credit Losses			$ 144,785,000	56,927,000	$ 56,522,000	$ 55,798,000
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent		22.00%
Non-acquired loans
Assests:
Allowance for credit losses		$ (34,049,000)
Equity:
Financing Receivable, Allowance for Credit Losses		34,049,000
Acquired loans
Assests:
Allowance for credit losses		(16,981,000)
Equity:
Financing Receivable, Allowance for Credit Losses		16,981,000
Purchased Credit Deteriorated Loans [Member]
Assests:
Allowance for credit losses		(3,408,000)
Equity:
Financing Receivable, Allowance for Credit Losses		3,408,000
ASU 2016-13
Assests:
Acquired Loans	[1]	1,723,000
Allowance for credit losses	[2]	(54,438,000)
Deferred tax assets	[3]	12,639,000
Accrued Interest Receivable - Loans	[1]	1,677,000
Liabilities:
Reserve for Loan Losses - Unfunded Commitments	[4]	6,421,000
Equity:
Retained Earnings (Accumulated Deficit)	[5]	(44,820,000)
Financing Receivable, Allowance for Credit Losses	[2]	54,438,000
As previously recorded by acquiree | ASU 2016-13
Assests:
Securities available for sale, at fair value (Cost of $1,915,461 and allowance for credit losses of $0 for March 31, 2020)		1,956,047,000
Non - Acquired Loans		9,252,831,000
Acquired Loans		2,118,940,000
Allowance for credit losses		(111,365,000)
Deferred tax assets		43,955,000
Accrued Interest Receivable - Loans		30,009,000
Liabilities:
Reserve for Loan Losses - Unfunded Commitments		6,756,000
Equity:
Retained Earnings (Accumulated Deficit)		635,075,000
Financing Receivable, Allowance for Credit Losses		111,365,000
Adjustments
Assests:
Allowance for credit losses				(111,365,000)
Equity:
Financing Receivable, Allowance for Credit Losses				111,365,000
Adjustments | ASU 2016-13
Assests:
Securities available for sale, at fair value (Cost of $1,915,461 and allowance for credit losses of $0 for March 31, 2020)		1,956,047,000
Non - Acquired Loans		9,252,831,000
Acquired Loans		2,117,209,000
Allowance for credit losses		(56,927,000)		(51,030,000)
Deferred tax assets		31,316,000
Accrued Interest Receivable - Loans		28,332,000
Liabilities:
Reserve for Loan Losses - Unfunded Commitments		335,000
Equity:
Retained Earnings (Accumulated Deficit)		679,895,000
Financing Receivable, Allowance for Credit Losses		$ 56,927,000		$ 51,030,000

[1] Accrued interest receivable from acquired credit impaired loans of $1,677 was reclassed to other assets and was offset by the reclass of the grossed up credit discount on acquired credit impaired loans of $3,408 that was moved to the ACL for the purchased credit deteriorated loans.

[2] This is the calculated adjustment to the ACL related to the adoption of ASC 326. Additional reserve related to non-acquired loans was $34,049, to acquired loans was $16,981 and to purchased credit deteriorated loans was $3,408.

[3] This is the effect of deferred tax assets related to the adjustment to the ACL from the adoption of ASC 326 using a 22% tax rate.

[4] This is the adjustment to the reserve for unfunded commitments related to the adoption of ASC 326.

[5] This is the net adjustment to retained earnings related to the adoption of ASC 326.