Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 8,836,721	$ 7,810,900
Financial and Nonfinancial Liabilities, Fair Value Disclosure	(52,013)	(19,029)
Derivative Financial Instruments, Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	(52,013)	(19,029)
U.S. Treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	77,180	70,325
U.S. Government agency and sponsored enterprise residential MBS
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	2,379,840	2,022,175
U.S. Government agency and sponsored enterprise commercial MBS
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	464,277	370,976
Private label residential mortgage-backed securities and CMOs
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	1,116,086	1,012,177
Private label commercial mortgage-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	2,043,620	1,724,684
Single family rental real estate-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	618,207	470,025
Collateralized loan obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	1,128,753	1,197,366
Non-mortgage asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	261,531	194,904
State and municipal obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	259,495	273,302
SBA securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	245,942	362,731
Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	88,697	60,572
Servicing Rights [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	7,291	7,977
Derivative Financial Instruments, Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	145,802	43,686
Fair Value, Inputs, Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	165,877	130,897
Fair Value, Inputs, Level 1 | U.S. Treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	77,180	70,325
Fair Value, Inputs, Level 1 | Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	88,697	60,572
Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	8,670,844	7,680,003
Financial and Nonfinancial Liabilities, Fair Value Disclosure	(52,013)	(19,029)
Fair Value, Inputs, Level 2 | Derivative Financial Instruments, Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	(52,013)	(19,029)
Fair Value, Inputs, Level 2 | U.S. Government agency and sponsored enterprise residential MBS
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	2,379,840	2,022,175
Fair Value, Inputs, Level 2 | U.S. Government agency and sponsored enterprise commercial MBS
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	464,277	370,976
Fair Value, Inputs, Level 2 | Private label residential mortgage-backed securities and CMOs
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	1,116,086	1,012,177
Fair Value, Inputs, Level 2 | Private label commercial mortgage-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	2,043,620	1,724,684
Fair Value, Inputs, Level 2 | Single family rental real estate-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	618,207	470,025
Fair Value, Inputs, Level 2 | Collateralized loan obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	1,128,753	1,197,366
Fair Value, Inputs, Level 2 | Non-mortgage asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	261,531	194,904
Fair Value, Inputs, Level 2 | State and municipal obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	259,495	273,302
Fair Value, Inputs, Level 2 | SBA securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	245,942	362,731
Fair Value, Inputs, Level 2 | Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 | Servicing Rights [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	7,291	7,977
Fair Value, Inputs, Level 2 | Derivative Financial Instruments, Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 145,802	$ 43,686