Acquisitions and Divestitures - Purchase Price Allocation (Details) - USD ($) $ in Thousands			3 Months Ended	9 Months Ended
		Nov. 30, 2017	Jun. 30, 2018	Sep. 30, 2018		Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Assets:
Cash and cash equivalents				$ 642,051		$ 639,073
Trading securities				1,930,991		1,416,345
Loans held-for-sale	[1]			725,651		699,377
Securities held-to-maturity				10,000		10,000
Loans				27,350,214	[2]	27,658,929	[2]	$ 20,166,091
Allowance for loan losses			$ (185,462)	(185,959)		(189,555)		(194,867)	$ (197,257)	$ (202,068)
CBF Goodwill				1,409,822		1,386,853		236,335		191,371
Other intangible assets				161,495		184,389
Premises and equipment				506,453		532,251
OREO	[3]			28,628		43,382
Other assets				1,883,077		1,723,189
Total assets				40,635,924		41,423,388
Liabilities:
Deposits				31,008,085		30,620,362
Securities sold under agreements to repurchase				678,510		656,602
Other short-term borrowings				1,069,912		2,626,213
Term borrowings				1,200,134		1,218,097
Other liabilities				552,921		549,234
Total liabilities				35,893,993		36,842,900
Consideration paid:
Goodwill				1,409,822		1,386,853		$ 236,335		$ 191,371
Capital Bank Financial Corporation
Assets:
CBF Goodwill				1,169,874
Assets As Recorded:
Cash and cash equivalents				205,999
Trading securities				0
Loans held-for-sale				124,918
Securities available-for-sale		$ 1,200,000		1,193,393
Securities held-to-maturity				0
Loans		7,300,000		7,276,544
Allowance for loan losses				0
Other intangible assets				141,207
Premises and equipment				231,001
OREO				33,613
Other assets				651,304
Total assets acquired		9,900,000		9,857,979
Liabilities As Recorded:
Deposits		8,100,000		8,140,102
Securities sold under agreements to repurchase				26,664
Other short-term borrowings				390,391
Term borrowings				187,169
Other liabilities				67,194
Total liabilities assumed				8,811,520
Net assets acquired				1,046,459
Consideration paid:
Equity				(1,746,724)
Cash		(423,600)	$ (46,000)	(469,609)
Total consideration paid		(2,200,000)		(2,216,333)
Goodwill				1,169,874
Capital Bank Financial Corporation | Purchase Accounting/Fair Value Adjustments
Assets:
Cash and cash equivalents				0		0
Trading securities				0		(4,758)
Loans held-for-sale				(9,085)		134,003
Securities available-for-sale				0		175,526
Securities held-to-maturity				0		(177,549)
Loans				867		(320,372)
Allowance for loan losses				0		45,711
CBF Goodwill				0		(231,292)
Other intangible assets				(2,593)		119,302
Premises and equipment				(2,351)		37,054
OREO				(315)		(9,149)
Other assets				(7,248)		41,320
Total assets				(20,725)		(190,204)
Liabilities:
Deposits				(642)		(849)
Securities sold under agreements to repurchase				0		0
Other short-term borrowings				0		0
Term borrowings				0		67,683
Other liabilities				2,908		4,291
Total liabilities				2,266		71,125
Net assets acquired				(22,991)		(261,329)
Consideration paid:
Goodwill				$ 0		$ (231,292)
Capital Bank Financial Corporation
Assets:
Cash and cash equivalents		205,999
Trading securities		4,758
Loans held-for-sale		0
Securities available-for-sale		1,017,867
Securities held-to-maturity		177,549
Loans		7,596,049
Allowance for loan losses		(45,711)
CBF Goodwill		231,292
Other intangible assets		24,498
Premises and equipment		196,298
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		119,486
Other liabilities		59,995
Total liabilities		8,738,129
Net assets acquired		1,330,779
Consideration paid:
Goodwill		$ 231,292

[1] September 30, 2018 and December 31, 2017 include $9.2 million and $11.7 million, respectively, of held-for-sale consumer mortgage loans secured by residential real estate in process of foreclosure.

[2] September 30, 2018 and December 31, 2017 include $20.8 million and $22.7 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.

[3] September 30, 2018 and December 31, 2017 include $11.0 million and $12.2 million, respectively, of foreclosed residential real estate.