Loans and Allowance for Loan Losses (Schedule of Current, Accruing Past Due and Nonaccrual Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Jan. 01, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	$ 39,549,847	$ 37,162,450
Non-accrual	129,748	99,848
Non-accrual, without an allowance	39,089
Total loans	39,648,824	37,187,814
Deferred fees and costs, net	99,000	25,400
FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		5,557,334
Loans	90,300		$ 9,290,000
Acquired Loans, ASC 310-30 | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	1,800
Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	78,038	65,797
Non-accrual, without an allowance	37,588
Total loans	20,014,151	16,769,370
Total commercial and industrial | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		1,842,331
Total commercial and industrial | Commercial, financial and agricultural
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	67,415	56,017
Non-accrual, without an allowance	27,950
Total loans	13,120,038	10,239,559
Total commercial and industrial | Commercial, financial and agricultural | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		1,019,135
Total commercial and industrial | Owner-occupied
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	10,623	9,780
Non-accrual, without an allowance	9,638
Total loans	6,894,113	6,529,811
Total commercial and industrial | Owner-occupied | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		823,196
Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	32,521	4,944
Non-accrual, without an allowance	1,501
Total loans	10,965,875	10,493,784
Total commercial real estate | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		1,856,170
Total commercial real estate | Investment properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	28,260	1,581
Non-accrual, without an allowance	0
Total loans	9,662,447	9,004,327
Total commercial real estate | Investment properties | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		1,736,608
Total commercial real estate | 1-4 family properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	2,135	2,253
Non-accrual, without an allowance	1,236
Total loans	655,038	780,015
Total commercial real estate | 1-4 family properties | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		41,401
Total commercial real estate | Land and development
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	2,126	1,110
Non-accrual, without an allowance	265
Total loans	648,390	709,442
Total commercial real estate | Land and development | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		78,161
Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	19,189	29,107
Non-accrual, without an allowance	0
Total loans	8,668,798	9,924,660
Total consumer | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		1,858,833
Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	7,433	11,369
Non-accrual, without an allowance	0
Total loans	5,658,525	5,546,368
Total consumer | Consumer mortgages | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		1,848,493
Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	10,297	12,034
Non-accrual, without an allowance	0
Total loans	1,615,207	1,713,157
Total consumer | Home equity lines | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		2,155
Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	0	0
Non-accrual, without an allowance	0
Total loans	264,829	268,841
Total consumer | Credit cards | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		0
Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Non-accrual	1,459	5,704
Non-accrual, without an allowance	0
Total loans	1,130,237	2,396,294
Total consumer | Other consumer loans | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
ASC 310-30 Loans		8,185
Current
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	39,422,671	31,442,999
Current | Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	19,879,223	14,815,380
Current | Total commercial and industrial | Commercial, financial and agricultural
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	13,009,877	9,124,285
Current | Total commercial and industrial | Owner-occupied
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	6,869,346	5,691,095
Current | Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	10,922,402	8,628,141
Current | Total commercial real estate | Investment properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	9,628,029	7,264,794
Current | Total commercial real estate | 1-4 family properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	649,225	733,984
Current | Total commercial real estate | Land and development
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	645,148	629,363
Current | Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	8,621,046	7,999,478
Current | Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	5,643,745	3,681,553
Current | Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,601,705	1,691,759
Current | Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	259,262	263,065
Current | Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,116,334	2,363,101
Accruing 30 to 89 Days Past Due
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	49,804	81,330
Accruing 30 to 89 Days Past Due | Acquired Loans, ASC 310-30 | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans	26,500
Accruing 30 to 89 Days Past Due | Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	18,098	44,080
Accruing 30 to 89 Days Past Due | Total commercial and industrial | Commercial, financial and agricultural
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	13,967	38,916
Accruing 30 to 89 Days Past Due | Total commercial and industrial | Owner-occupied
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	4,131	5,164
Accruing 30 to 89 Days Past Due | Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	8,295	4,225
Accruing 30 to 89 Days Past Due | Total commercial real estate | Investment properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	5,620	1,344
Accruing 30 to 89 Days Past Due | Total commercial real estate | 1-4 family properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	2,092	2,073
Accruing 30 to 89 Days Past Due | Total commercial real estate | Land and development
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	583	808
Accruing 30 to 89 Days Past Due | Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	23,411	33,025
Accruing 30 to 89 Days Past Due | Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	6,475	4,223
Accruing 30 to 89 Days Past Due | Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	3,176	7,038
Accruing 30 to 89 Days Past Due | Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,894	3,076
Accruing 30 to 89 Days Past Due | Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	11,866	18,688
Accruing 90 to 149 Days Past Due
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	7,512	6,303
Accruing 90 to 149 Days Past Due | Acquired Loans, ASC 310-30 | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans	9,600
Accruing 90 to 149 Days Past Due | Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,204	1,782
Accruing 90 to 149 Days Past Due | Total commercial and industrial | Commercial, financial and agricultural
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	829	1,206
Accruing 90 to 149 Days Past Due | Total commercial and industrial | Owner-occupied
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	375	576
Accruing 90 to 149 Days Past Due | Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,156	304
Accruing 90 to 149 Days Past Due | Total commercial real estate | Investment properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	538	0
Accruing 90 to 149 Days Past Due | Total commercial real estate | 1-4 family properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	350	304
Accruing 90 to 149 Days Past Due | Total commercial real estate | Land and development
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	268	0
Accruing 90 to 149 Days Past Due | Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	5,152	4,217
Accruing 90 to 149 Days Past Due | Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	872	730
Accruing 90 to 149 Days Past Due | Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	29	171
Accruing 90 to 149 Days Past Due | Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	3,673	2,700
Accruing 90 to 149 Days Past Due | Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	578	616
Total Accruing Past Due
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	57,316	87,633
Total Accruing Past Due | Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	19,302	45,862
Total Accruing Past Due | Total commercial and industrial | Commercial, financial and agricultural
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	14,796	40,122
Total Accruing Past Due | Total commercial and industrial | Owner-occupied
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	4,506	5,740
Total Accruing Past Due | Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	9,451	4,529
Total Accruing Past Due | Total commercial real estate | Investment properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	6,158	1,344
Total Accruing Past Due | Total commercial real estate | 1-4 family properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	2,442	2,377
Total Accruing Past Due | Total commercial real estate | Land and development
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	851	808
Total Accruing Past Due | Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	28,563	37,242
Total Accruing Past Due | Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	7,347	4,953
Total Accruing Past Due | Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	3,205	7,209
Total Accruing Past Due | Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	5,567	5,776
Total Accruing Past Due | Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	$ 12,444	$ 19,304