Loans and Allowance for Credit Losses - Allowance for Credit Losses (Details) - USD ($) $ in Thousands		3 Months Ended
Jan. 01, 2020	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 94,777	$ 94,777	$ 83,575
Impact of adopting ASC 326		34,300
Charged-off loans		(11,693)	(6,068)
Recovery of previously charged-off loans		1,538	2,503
Provision for Loan and Lease Losses		99,741	7,184
Ending Balance		222,465	87,194
Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adopting ASC 326	38,102
Commercial real estate- owner occupied
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	13,406	13,406	11,297
Charged-off loans		(1,561)	(521)
Recovery of previously charged-off loans		145	60
Provision for Loan and Lease Losses		11,380	1,782
Ending Balance		23,634	12,618
Commercial real estate- owner occupied \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adopting ASC 326	264
Commercial real estate- Non-owner occupied
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	19,963	19,963	15,649
Charged-off loans		(261)	(13)
Recovery of previously charged-off loans		93	12
Provision for Loan and Lease Losses		17,059	1,901
Ending Balance		32,114	17,549
Commercial real estate- Non-owner occupied \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adopting ASC 326	(4,740)
Consumer real estate – mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	8,054	8,054	7,670
Charged-off loans		(930)	(350)
Recovery of previously charged-off loans		190	369
Provision for Loan and Lease Losses		4,655	680
Ending Balance		32,998	8,369
Consumer real estate – mortgage \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adopting ASC 326	21,029
Construction and land development
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	12,662	12,662	11,128
Charged-off loans		0	0
Recovery of previously charged-off loans		43	122
Provision for Loan and Lease Losses		29,350	(335)
Ending Balance		38,911	10,915
Construction and land development \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adopting ASC 326	(3,144)
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	36,112	36,112	31,731
Charged-off loans		(7,734)	(3,352)
Recovery of previously charged-off loans		748	1,598
Provision for Loan and Lease Losses		35,894	2,722
Ending Balance		88,060	32,699
Commercial and industrial \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adopting ASC 326	23,040
Consumer and other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3,595	3,595	5,423
Charged-off loans		(1,207)	(1,832)
Recovery of previously charged-off loans		319	342
Provision for Loan and Lease Losses		1,403	870
Ending Balance		6,748	4,803
Consumer and other \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adopting ASC 326	2,638
Unallocated
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	985	985	677
Charged-off loans		0	0
Recovery of previously charged-off loans		0	0
Provision for Loan and Lease Losses		0	(436)
Ending Balance		$ 0	$ 241
Unallocated \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adopting ASC 326	$ (985)

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of increase (decrease) in allowance for credit loss on financing receivable.

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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Amount of writeoff of financing receivable, charged against allowance for credit loss.

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