Fair Value Measurements - Assets and Liabilities Measured and Recorded at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	$ 7,198,608	$ 5,235,591
Securities available-for-sale, at fair value	7,198,608	5,235,591
Equity Securities, FV-NI	13,063	6,147
Derivative Liability	844	1,150
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity warrants		4,520
Government agency and government-sponsored enterprise pass through securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	1,257,628	1,281,877
Government agency and government-sponsored enterprise collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	1,142,398	1,219,880
Private label collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	96,922	116,946
Collateralized loan obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	382,043	135,876
Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	1,817,499	1,531,617
Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	149,583	166,546
SBA asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	36,028	41,627
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	508,708	311,889
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	877,153	5,302
Private label commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	378,235	82,957
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	7,198,608
Equity warrants	4,391	4,520
Interest rate and economic contracts	3,327	4,230
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale, at fair value	877,153	5,302
Equity warrants	0	0
Interest rate and economic contracts	0	0
Equity Securities, FV-NI	13,063	6,147
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale, at fair value	6,295,468	5,199,917
Equity warrants	0	0
Interest rate and economic contracts	3,327	4,230
Equity Securities, FV-NI	0	0
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale, at fair value	25,987	30,372
Equity warrants	4,391	4,520
Interest rate and economic contracts	0	0
Equity Securities, FV-NI	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise pass through securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	552,411	341,074
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise pass through securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise pass through securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	552,411	341,074
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise pass through securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	1,142,398	1,219,880
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise collateralized mortgage obligations | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise collateralized mortgage obligations | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	1,142,398	1,219,880
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise collateralized mortgage obligations | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Private label collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	96,922	116,946
Fair Value, Measurements, Recurring | Private label collateralized mortgage obligations | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Private label collateralized mortgage obligations | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	92,778	112,299
Fair Value, Measurements, Recurring | Private label collateralized mortgage obligations | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	4,144	4,647
Fair Value, Measurements, Recurring | Collateralized loan obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	382,043	135,876
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	382,043	135,876
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	1,817,499	1,531,617
Fair Value, Measurements, Recurring | Municipal securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Municipal securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	1,817,499	1,531,617
Fair Value, Measurements, Recurring | Municipal securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	1,257,628	1,281,877
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise commercial mortgage-backed securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise commercial mortgage-backed securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	1,257,628	1,281,877
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise commercial mortgage-backed securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	149,583	166,546
Fair Value, Measurements, Recurring | Asset-backed Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Asset-backed Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	149,583	166,546
Fair Value, Measurements, Recurring | Asset-backed Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | SBA asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	36,028	41,627
Fair Value, Measurements, Recurring | SBA asset-backed securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | SBA asset-backed securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	36,028	41,627
Fair Value, Measurements, Recurring | SBA asset-backed securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	508,708	311,889
Fair Value, Measurements, Recurring | Corporate debt securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Corporate debt securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	508,708	311,889
Fair Value, Measurements, Recurring | Corporate debt securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	877,153	5,302
Fair Value, Measurements, Recurring | U.S. Treasury securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	877,153	5,302
Fair Value, Measurements, Recurring | U.S. Treasury securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | U.S. Treasury securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Private label commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	378,235	82,957
Fair Value, Measurements, Recurring | Private label commercial MBS | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	0	0
Fair Value, Measurements, Recurring | Private label commercial MBS | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	356,392	57,232
Fair Value, Measurements, Recurring | Private label commercial MBS | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	$ 21,843	$ 25,725