Derivatives and Hedging - Cash Flow Hedges (Details) - USD ($)		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts presented in the unaudited condensed consolidated statements of income		$ 715,476,000	$ 800,488,000
Total amounts presented in the unaudited condensed consolidated statements of income		$ 21,176,000	37,626,000
Derivatives designated as hedging instrument | Fair value hedges | Interest rate swap
Derivative Instruments, Gain (Loss) [Line Items]
Cash flow hedges, weighted average expected remaining term		3 years 25 days
Derivatives designated as hedging instrument | Cash flow hedges | Interest rate swap
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on discontinuation of interest rate cash flow hedge due to forecasted transaction probable of not occurring, net		$ 0	0
Cash flow hedges not terminated, net fair value		$ (5,000,000)
Cash flow hedges, weighted average expected remaining term		2 years 9 months 63 days
Cash flow hedge gain (loss) to be reclassified within twelve months		$ 110,900,000
Maximum length of time hedged in interest rate cash flow hedge		3 years 8 months 68 days
Interest and Fees on Loans
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts presented in the unaudited condensed consolidated statements of income		$ 715,476,000	800,488,000
Interest and Fees on Loans | Derivatives designated as hedging instrument | Fair value hedges
Gains (losses) on fair value hedging relationships:
Net income (expense) recognized on fair value hedges		0	0
Interest and Fees on Loans | Derivatives designated as hedging instrument | Fair value hedges | Interest rate contracts
Gains (losses) on fair value hedging relationships:
Amounts related to interest settlements and amortization on derivatives		0	0
Recognized on derivatives		0	0
Recognized on hedged items		0	0
Interest and Fees on Loans | Derivatives designated as hedging instrument | Cash flow hedges
Gain (losses) on cash flow hedging relationships:
Net income (expense) recognized on cash flow hedges	[1]	5,459,000	(1,210,000)
Interest and Fees on Loans | Derivatives designated as hedging instrument | Cash flow hedges | Interest rate contracts
Gain (losses) on cash flow hedging relationships:
Realized losses reclassified from AOCI into net income	[1],[2]	5,459,000	(1,210,000)
Interest on FHLB and other borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts presented in the unaudited condensed consolidated statements of income		21,176,000	37,626,000
Interest on FHLB and other borrowings | Derivatives designated as hedging instrument | Fair value hedges
Gains (losses) on fair value hedging relationships:
Net income (expense) recognized on fair value hedges		10,138,000	(957,000)
Interest on FHLB and other borrowings | Derivatives designated as hedging instrument | Fair value hedges | Interest rate contracts
Gains (losses) on fair value hedging relationships:
Amounts related to interest settlements and amortization on derivatives		3,365,000	(2,348,000)
Recognized on derivatives		105,944,000	24,034,000
Recognized on hedged items		(99,171,000)	(22,643,000)
Interest on FHLB and other borrowings | Derivatives designated as hedging instrument | Cash flow hedges
Gain (losses) on cash flow hedging relationships:
Net income (expense) recognized on cash flow hedges	[1]	(419,000)	(169,000)
Interest on FHLB and other borrowings | Derivatives designated as hedging instrument | Cash flow hedges | Interest rate contracts
Gain (losses) on cash flow hedging relationships:
Realized losses reclassified from AOCI into net income	[1],[2]	$ (419,000)	$ (169,000)

[1] See Note 10, Comprehensive Income, for gain or loss recognized for cash flow hedges in accumulated other comprehensive income.

[2] Pre-tax