Fair Value of Assets & Liabilities - Nonrecurring Fair Value Measurements (Details) - USD ($) $ in Thousands		Sep. 30, 2018		Dec. 31, 2017		Sep. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale (elected fair value)		$ 16,418		$ 20,881
Loans, net of unearned income		27,350,214	[1]	27,658,929	[1]	$ 20,166,091
OREO	[2]	28,628		43,382
Non Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net of unearned income		26,995		26,666
OREO		25,726		39,566
Other assets		23,329		26,521
Non Recurring | Loans held-for-sale—first mortgages
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale (elected fair value)		542		618
Non Recurring | Loans held-for-sale—SBAs and USDA
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale (elected fair value)		619,160		466,977
Non Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net of unearned income		0		0
OREO		0		0
Other assets		0		0
Non Recurring | Level 1 | Loans held-for-sale—first mortgages
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale (elected fair value)		0		0
Non Recurring | Level 1 | Loans held-for-sale—SBAs and USDA
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale (elected fair value)		0		0
Non Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net of unearned income		0		0
OREO		0		0
Other assets		0		0
Non Recurring | Level 2 | Loans held-for-sale—first mortgages
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale (elected fair value)		0		0
Non Recurring | Level 2 | Loans held-for-sale—SBAs and USDA
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale (elected fair value)		618,142		465,504
Non Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net of unearned income		26,995		26,666
OREO		25,726		39,566
Other assets		23,329		26,521
Non Recurring | Level 3 | Loans held-for-sale—first mortgages
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale (elected fair value)		542		618
Non Recurring | Level 3 | Loans held-for-sale—SBAs and USDA
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale (elected fair value)		$ 1,018		$ 1,473

[1] 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.

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