Acquisitions and Divestitures - Purchase Price Allocation (Details) - USD ($) $ in Thousands				3 Months Ended	7 Months Ended	12 Months Ended
		Nov. 30, 2017	Apr. 03, 2017	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill, Acquired During Period						$ 0		$ 45,934		$ 1,195,482
Assets:
Cash and due from banks						633,728		781,291
Interest-bearing cash						482,405		1,277,611
Trading securities						1,346,207		1,448,168
Loans held-for-sale	[1]					593,790		679,149
Securities held-to-maturity (Note 3)						10,000		10,000
Loans, net of unearned income						31,061,111	[2]	27,535,532	[2]	27,658,929
Allowance for loan losses						(200,307)		(180,424)		(189,555)	$ (202,068)
Goodwill						1,432,787		1,432,787		1,386,853	191,371
Other intangible assets						130,200		155,034
Premises and equipment, net						455,006		494,041
Other real estate owned (OREO)	[3]					17,838		25,290
Other assets						2,046,338		1,802,939
Total assets						43,310,900		40,832,258
Liabilities:
Deposits						32,429,535		32,682,992
Securities sold under agreements to repurchase						716,925		762,592
Other short-term borrowings						2,253,045		114,764
Fixed income payables						49,535		9,572
Term borrowings (Note 10)						791,368		1,170,963
Other liabilities						873,079		580,335
Total liabilities						38,234,892		36,046,878
Consideration paid:
Goodwill						$ 1,432,787		1,432,787		1,386,853	$ 191,371
Capital Bank Financial Corporation
Business Acquisition [Line Items]
Goodwill, Acquired During Period		$ 0
Assets:
Goodwill		1,192,839
Assets As Recorded:
Cash and cash equivalents		205,999
Trading securities		0
Loans held-for-sale		122,969
Securities available-for-sale		1,193,393
Securities held-to-maturity		0
Loans		7,276,544
Allowance for loan losses		0
Other intangible assets		141,207
Premises and equipment		223,882
OREO		33,613
Other assets		636,130
Total assets acquired		9,833,737
Liabilities As Recorded:
Deposits		8,140,102
Securities sold under agreements to repurchase		26,664
Other short-term borrowings		390,391
Term borrowings		187,169
Other liabilities		65,917
Total liabilities assumed		8,810,243
Net assets acquired		1,023,494
Consideration paid:
Equity		(1,746,718)
Cash		(423,600)		$ (46,000)	$ (469,615)
Total consideration paid		(2,216,333)
Goodwill		1,192,839
Capital Bank Financial Corporation | Purchase Accounting/Fair Value Adjustments
Assets:
Cash and due from banks								0		0
Trading securities								0		(4,758)
Loans held-for-sale								(11,034)		134,003
Securities available-for-sale								0		175,526
Securities held-to-maturity (Note 3)								0		(177,549)
Loans, net of unearned income								867		(320,372)
Allowance for loan losses								0		45,711
Goodwill								0		(231,292)
Other intangible assets								(2,593)		119,302
Premises and equipment, net								(9,470)		37,054
Other real estate owned (OREO)								(315)		(9,149)
Other assets								(22,422)		41,320
Total assets								(44,967)		(190,204)
Liabilities:
Deposits								(642)		(849)
Securities sold under agreements to repurchase								0		0
Other short-term borrowings								0		0
Term borrowings (Note 10)								0		67,683
Other liabilities								1,631		4,291
Total liabilities								989		71,125
Net assets acquired								(45,956)		(261,329)
Consideration paid:
Goodwill								$ 0		$ (231,292)
Coastal Securities, Inc
Assets:
Goodwill			$ 44,964
Assets As Recorded:
Cash and cash equivalents			7,502
Interest-bearing cash			4,132
Trading securities			139,082
Loans held-for-sale			236,088
Investment securities			1,413
Other intangible assets			27,300
Premises and equipment			1,229
Other assets			1,672
Total assets acquired			418,418
Liabilities As Recorded:
Securities sold under agreements to repurchase			201,595
Other short-term borrowings			33,509
Fixed income payables			96,489
Other liabilities			316
Total liabilities assumed			331,909
Net assets acquired			86,509
Consideration paid:
Cash			(131,473)
Goodwill			44,964
Coastal Securities, Inc | Purchase Accounting/Fair Value Adjustments
Assets:
Cash and due from banks			0
Interest-bearing cash			0
Trading securities			(284,580)
Loans held-for-sale			236,088
Investment securities			1,413
Other intangible assets			27,300
Premises and equipment, net			0
Other assets			14
Total assets			(19,765)
Liabilities:
Securities sold under agreements to repurchase			0
Other short-term borrowings			0
Fixed income payables			(47,158)
Other liabilities			(642)
Total liabilities			(47,800)
Net assets acquired			28,035
Capital Bank Financial Corporation
Assets:
Cash and due from banks		205,999
Trading securities		4,758
Loans held-for-sale		0
Securities available-for-sale		1,017,867
Securities held-to-maturity (Note 3)		177,549
Loans, net of unearned income		7,596,049
Allowance for loan losses		(45,711)
Goodwill		231,292
Other intangible assets		24,498
Premises and equipment, net		196,298
Other real estate owned (OREO)		43,077
Other assets		617,232
Total assets		10,068,908
Liabilities:
Deposits		8,141,593
Securities sold under agreements to repurchase		26,664
Other short-term borrowings		390,391
Term borrowings (Note 10)		119,486
Other liabilities		59,995
Total liabilities		8,738,129
Net assets acquired		1,330,779
Consideration paid:
Goodwill		$ 231,292
Coastal Securities, Inc
Assets:
Cash and due from banks			7,502
Interest-bearing cash			4,132
Trading securities			423,662
Loans held-for-sale			0
Investment securities			0
Other intangible assets			0
Premises and equipment, net			1,229
Other assets			1,658
Total assets			438,183
Liabilities:
Securities sold under agreements to repurchase			201,595
Other short-term borrowings			33,509
Fixed income payables			143,647
Other liabilities			958
Total liabilities			379,709
Net assets acquired			$ 58,474

[1] December 31, 2019 and 2018 include $6.8 million and $8.4 million, respectively, of held-for-sale consumer mortgage loans secured by residential real estate in process of foreclosure.

[2] December 31, 2019 and 2018 include $18.8 million and $28.6 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.

[3] December 31, 2019 and 2018 include $9.2 million and $9.7 million, respectively, of foreclosed residential real estate.