Loans and Allowance for Loan Losses (Schedule of Current, Accruing Past Due and Nonaccrual Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 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	$ 38,258,024	$ 37,162,450
Non-accrual	124,805	99,848
Non-accrual, without an allowance	31,482
Total loans	38,283,556	37,187,814
Deferred fees and costs, net	25,500	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 [Member] | 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	85,981	65,797
Non-accrual, without an allowance	30,663
Total loans	17,661,442	16,782,670
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	78,263	56,017
Non-accrual, without an allowance	21,024
Total loans	11,018,155	10,252,859
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	7,718	9,780
Non-accrual, without an allowance	9,639
Total loans	6,643,287	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	6,472	4,944
Non-accrual, without an allowance	265
Total loans	10,671,201	10,480,484
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	2,212	1,581
Non-accrual, without an allowance	0
Total loans	9,257,791	9,042,679
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	2,325	2,253
Non-accrual, without an allowance	0
Total loans	751,468	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	1,935	1,110
Non-accrual, without an allowance	265
Total loans	661,942	657,790
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	32,352	29,107
Non-accrual, without an allowance	554
Total loans	9,950,913	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	13,017	11,369
Non-accrual, without an allowance	554
Total loans	5,608,121	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	12,475	12,034
Non-accrual, without an allowance	0
Total loans	1,778,862	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	261,581	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	6,860	5,704
Non-accrual, without an allowance	0
Total loans	2,302,349	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	38,044,034	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	17,511,689	14,828,680
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	10,896,890	9,137,585
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	6,614,799	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	10,655,513	8,614,841
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	9,252,438	7,303,146
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	744,451	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	658,624	577,711
Current | Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	9,876,832	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	5,583,714	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	1,759,571	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	256,445	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	2,277,102	2,363,101
Accruing 30 to 89 Days Pat Due
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	76,837	81,330
Accruing 30 to 89 Days Pat Due | Acquired Loans, ASC 310-30 [Member] | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans	26,500
Accruing 30 to 89 Days Pat Due | Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	31,428	44,080
Accruing 30 to 89 Days Pat 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	21,149	38,916
Accruing 30 to 89 Days Pat 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	10,279	5,164
Accruing 30 to 89 Days Pat Due | Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	8,668	4,225
Accruing 30 to 89 Days Pat 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	3,056	1,344
Accruing 30 to 89 Days Pat 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	4,636	2,073
Accruing 30 to 89 Days Pat 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	976	808
Accruing 30 to 89 Days Pat Due | Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	36,741	33,025
Accruing 30 to 89 Days Pat Due | Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	10,836	4,223
Accruing 30 to 89 Days Pat Due | Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	5,873	7,038
Accruing 30 to 89 Days Pat Due | Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	2,465	3,076
Accruing 30 to 89 Days Pat Due | Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	17,567	18,688
Accruing 90 to 149 Days Pat Due
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	6,398	6,303
Accruing 90 to 149 Days Pat Due | Acquired Loans, ASC 310-30 [Member] | FCB Financial Holdings, Inc.
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans	9,600
Accruing 90 to 149 Days Pat Due | Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,681	1,782
Accruing 90 to 149 Days Pat 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 Pat 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	852	576
Accruing 90 to 149 Days Pat Due | Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	283	304
Accruing 90 to 149 Days Pat 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	85	0
Accruing 90 to 149 Days Pat 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	56	304
Accruing 90 to 149 Days Pat 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	142	0
Accruing 90 to 149 Days Pat Due | Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	4,434	4,217
Accruing 90 to 149 Days Pat Due | Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	0	730
Accruing 90 to 149 Days Pat Due | Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	943	171
Accruing 90 to 149 Days Pat Due | Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	2,671	2,700
Accruing 90 to 149 Days Pat Due | Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	820	616
Total Accruing Past Due
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	83,235	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	33,109	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	21,978	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	11,131	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	8,951	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	3,141	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	4,692	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	1,118	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	41,175	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	10,836	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	6,816	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	5,136	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	$ 18,387	$ 19,304