Fair Value Measurements (Assets for which Nonrecurring Changes in Fair Value have been Recorded) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 9,436,783		$ 9,436,783		$ 7,810,900
Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	9,258,267		9,258,267		$ 7,680,003
OREO and Repossessed Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	3,803	$ 1,638	3,803	$ 1,638
Losses from Nonrecurring Fair Value Changes	(30)	(2,376)	(390)	(2,372)
OREO and Repossessed Assets [Member] | Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	3,803	1,638	3,803	1,638
OREO and Repossessed Assets [Member] | Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0	0	0
Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	74,661	21,104	74,661	21,104
Losses from Nonrecurring Fair Value Changes	(14,513)	(2,351)	(56,737)	(2,265)
Impaired Loans [Member] | Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	74,661	21,104	74,661	21,104
Impaired Loans [Member] | Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	$ 0	0	$ 0
Property Subject to Operating Lease [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	277		277
Losses from Nonrecurring Fair Value Changes	0		(691)
Property Subject to Operating Lease [Member] | Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 277		$ 277