Fair Value Measurements (Fair Value Assets And Liabilities Measured On Recurring and Nonrecurring Basis) (Detail) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		$ 3,016,631	$ 2,925,833
Gross derivative instruments, before netting (1)		355,222	133,158
Loans held for sale (valued under fair value option $22,147 and $35,750)		22,147	35,750
Financial liabilities held at fair value:
Derivative liability		1,154	7,163
Agency CMO [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		204,830	185,801
Agency MBS [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		1,612,818	1,612,164
Agency CMBS [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		697,682	581,552
Non-agency CMBS [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		409,023	431,871
CLO [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		81,398	92,205
Corporate debt securities [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		10,880	22,240
Fair Value, Recurring [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		3,016,631	2,925,833
Alternative investments (2)		5,701	5,701
Total financial assets held at fair value		3,449,633	3,118,101
Financial liabilities held at fair value:
Derivative liability	[1]	18,803	13,813
Fair Value, Recurring [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member]
Financial assets held at fair value:
Alternative investments (2)		0	0
Total financial assets held at fair value		4,798	5,108
Financial liabilities held at fair value:
Derivative liability	[1]	759	611
Fair Value, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		3,016,631	2,925,833
Alternative investments (2)		0	0
Total financial assets held at fair value		3,439,134	3,107,292
Financial liabilities held at fair value:
Derivative liability	[1]	18,044	13,202
Fair Value, Recurring [Member] | Derivative instruments [Member]
Financial assets held at fair value:
Gross derivative instruments, before netting (1)	[1]	401,164	146,037
Fair Value, Recurring [Member] | Derivative instruments [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member]
Financial assets held at fair value:
Gross derivative instruments, before netting (1)	[1]	808	328
Fair Value, Recurring [Member] | Derivative instruments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets held at fair value:
Gross derivative instruments, before netting (1)	[1]	400,356	145,709
Fair Value, Recurring [Member] | Investments Held In Rabbi Trust [Member]
Financial assets held at fair value:
Other assets		3,990	4,780
Fair Value, Recurring [Member] | Investments Held In Rabbi Trust [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member]
Financial assets held at fair value:
Other assets		3,990	4,780
Fair Value, Recurring [Member] | Loan Origination Commitments [Member]
Financial assets held at fair value:
Loans held for sale (valued under fair value option $22,147 and $35,750)		22,147	35,750
Fair Value, Recurring [Member] | Loan Origination Commitments [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member]
Financial assets held at fair value:
Loans held for sale (valued under fair value option $22,147 and $35,750)		0	0
Fair Value, Recurring [Member] | Loan Origination Commitments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets held at fair value:
Loans held for sale (valued under fair value option $22,147 and $35,750)		22,147	35,750
Fair Value, Recurring [Member] | Agency CMO [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		204,830	185,801
Fair Value, Recurring [Member] | Agency CMO [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		204,830	185,801
Fair Value, Recurring [Member] | Agency MBS [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		1,612,818	1,612,164
Fair Value, Recurring [Member] | Agency MBS [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		1,612,818	1,612,164
Fair Value, Recurring [Member] | Agency CMBS [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		697,682	581,552
Fair Value, Recurring [Member] | Agency CMBS [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		0	0
Fair Value, Recurring [Member] | Agency CMBS [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		697,682	581,552
Fair Value, Recurring [Member] | Agency CMBS [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		0	0
Fair Value, Recurring [Member] | Non-agency CMBS [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		409,023	431,871
Fair Value, Recurring [Member] | Non-agency CMBS [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		0	0
Fair Value, Recurring [Member] | Non-agency CMBS [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		409,023	431,871
Fair Value, Recurring [Member] | Non-agency CMBS [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		0	0
Fair Value, Recurring [Member] | CLO [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		81,398	92,205
Fair Value, Recurring [Member] | CLO [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		81,398	92,205
Fair Value, Recurring [Member] | Corporate debt securities [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		10,880	22,240
Fair Value, Recurring [Member] | Corporate debt securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets held at fair value:
Investment securities available-for-sale, at fair value		$ 10,880	$ 22,240

[1] or information relating to the impact of netting derivative assets and derivative liabilities as well as the impact from offsetting cash collateral paid to the same derivative counterparties see Note 13: Derivative Financial Instruments.(2)Alternative investments are recorded at NAV. Assets measured at NAV are not classified within the fair value hierarchy.