Fair Value Measurements (Fair Value Assets And Liabilities Measured On Recurring and Nonrecurring Basis) (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financial Assets:
Total available-for-sale investment securities	$ 8,744,897	$ 4,234,854
Asset derivatives	47,388	133,481
Value under fair value options	1,333	4,694
Financial Liabilities:
Liability derivatives	110,443	13,301
U.S. Treasury notes
Financial Assets:
Total available-for-sale investment securities	732,425	396,966
Government agency debentures
Financial Assets:
Total available-for-sale investment securities	217,219
Municipal bonds and notes
Financial Assets:
Total available-for-sale investment securities	1,894,537
Agency CMO
Financial Assets:
Total available-for-sale investment securities	79,513	90,384
Agency MBS
Financial Assets:
Total available-for-sale investment securities	2,574,569	1,593,403
Agency CMBS
Financial Assets:
Total available-for-sale investment securities	1,583,820	1,232,541
Non-agency CMBS
Financial Assets:
Total available-for-sale investment securities	864,157	886,263
CLO
Financial Assets:
Total available-for-sale investment securities	14,233	21,847
Corporate debt securities
Financial Assets:
Total available-for-sale investment securities	767,044	13,450
Other
Financial Assets:
Total available-for-sale investment securities	17,380
Fair Value, Recurring
Financial Assets:
Total available-for-sale investment securities	8,744,897	4,234,854
Alternative investments	73,185	27,732
Total financial assets	8,940,388	4,429,813
Financial Liabilities:
Liability derivatives	117,324	21,784
Fair Value, Recurring | Level 1
Financial Assets:
Total available-for-sale investment securities	732,425	396,966
Alternative investments	1,131	1,877
Total financial assets	747,380	402,446
Financial Liabilities:
Liability derivatives	217	141
Fair Value, Recurring | Level 2
Financial Assets:
Total available-for-sale investment securities	8,012,472	3,837,888
Alternative investments	0	0
Total financial assets	8,120,954	4,001,512
Financial Liabilities:
Liability derivatives	117,107	21,643
Fair Value, Recurring | Level 3
Financial Assets:
Total available-for-sale investment securities	0	0
Alternative investments	0	0
Total financial assets	0	0
Financial Liabilities:
Liability derivatives	0	0
Fair Value, Recurring | Derivative instruments
Financial Assets:
Asset derivatives	107,571	159,117
Fair Value, Recurring | Derivative instruments | Level 1
Financial Assets:
Asset derivatives	422	187
Fair Value, Recurring | Derivative instruments | Level 2
Financial Assets:
Asset derivatives	107,149	158,930
Fair Value, Recurring | Derivative instruments | Level 3
Financial Assets:
Asset derivatives	0	0
Fair Value, Recurring | Loan Origination Commitments
Financial Assets:
Value under fair value options	1,333	4,694
Fair Value, Recurring | Loan Origination Commitments | Level 1
Financial Assets:
Value under fair value options	0	0
Fair Value, Recurring | Loan Origination Commitments | Level 2
Financial Assets:
Value under fair value options	1,333	4,694
Fair Value, Recurring | Loan Origination Commitments | Level 3
Financial Assets:
Value under fair value options	0	0
Fair Value, Recurring | Investments Held In Rabbi Trust
Financial Assets:
Other assets	13,402	3,416
Fair Value, Recurring | Investments Held In Rabbi Trust | Level 1
Financial Assets:
Other assets	13,402	3,416
Fair Value, Recurring | Investments Held In Rabbi Trust | Level 2
Financial Assets:
Other assets	0	0
Fair Value, Recurring | Investments Held In Rabbi Trust | Level 3
Financial Assets:
Other assets	0	0
Fair Value, Recurring | U.S. Treasury notes
Financial Assets:
Total available-for-sale investment securities	732,425	396,966
Fair Value, Recurring | U.S. Treasury notes | Level 1
Financial Assets:
Total available-for-sale investment securities	732,425	396,966
Fair Value, Recurring | U.S. Treasury notes | Level 2
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | U.S. Treasury notes | Level 3
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | Government agency debentures
Financial Assets:
Total available-for-sale investment securities	217,219
Fair Value, Recurring | Government agency debentures | Level 1
Financial Assets:
Total available-for-sale investment securities	0
Fair Value, Recurring | Government agency debentures | Level 2
Financial Assets:
Total available-for-sale investment securities	217,219
Fair Value, Recurring | Government agency debentures | Level 3
Financial Assets:
Total available-for-sale investment securities	0
Fair Value, Recurring | Municipal bonds and notes
Financial Assets:
Total available-for-sale investment securities	1,894,537
Fair Value, Recurring | Municipal bonds and notes | Level 1
Financial Assets:
Total available-for-sale investment securities	0
Fair Value, Recurring | Municipal bonds and notes | Level 2
Financial Assets:
Total available-for-sale investment securities	1,894,537
Fair Value, Recurring | Municipal bonds and notes | Level 3
Financial Assets:
Total available-for-sale investment securities	0
Fair Value, Recurring | Agency CMO
Financial Assets:
Total available-for-sale investment securities	79,513	90,384
Fair Value, Recurring | Agency CMO | Level 1
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | Agency CMO | Level 2
Financial Assets:
Total available-for-sale investment securities	79,513	90,384
Fair Value, Recurring | Agency CMO | Level 3
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | Agency MBS
Financial Assets:
Total available-for-sale investment securities	2,574,569	1,593,403
Fair Value, Recurring | Agency MBS | Level 1
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | Agency MBS | Level 2
Financial Assets:
Total available-for-sale investment securities	2,574,569	1,593,403
Fair Value, Recurring | Agency MBS | Level 3
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | Agency CMBS
Financial Assets:
Total available-for-sale investment securities	1,583,820	1,232,541
Fair Value, Recurring | Agency CMBS | Level 1
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | Agency CMBS | Level 2
Financial Assets:
Total available-for-sale investment securities	1,583,820	1,232,541
Fair Value, Recurring | Agency CMBS | Level 3
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | Non-agency CMBS
Financial Assets:
Total available-for-sale investment securities	864,157	886,263
Fair Value, Recurring | Non-agency CMBS | Level 1
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | Non-agency CMBS | Level 2
Financial Assets:
Total available-for-sale investment securities	864,157	886,263
Fair Value, Recurring | Non-agency CMBS | Level 3
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | CLO
Financial Assets:
Total available-for-sale investment securities	14,233	21,847
Fair Value, Recurring | CLO | Level 1
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | CLO | Level 2
Financial Assets:
Total available-for-sale investment securities	14,233	21,847
Fair Value, Recurring | CLO | Level 3
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | Corporate debt securities
Financial Assets:
Total available-for-sale investment securities	767,044	13,450
Fair Value, Recurring | Corporate debt securities | Level 1
Financial Assets:
Total available-for-sale investment securities	0	0
Fair Value, Recurring | Corporate debt securities | Level 2
Financial Assets:
Total available-for-sale investment securities	767,044	13,450
Fair Value, Recurring | Corporate debt securities | Level 3
Financial Assets:
Total available-for-sale investment securities	0	$ 0
Fair Value, Recurring | Other
Financial Assets:
Total available-for-sale investment securities	17,380
Fair Value, Recurring | Other | Level 1
Financial Assets:
Total available-for-sale investment securities	0
Fair Value, Recurring | Other | Level 2
Financial Assets:
Total available-for-sale investment securities	17,380
Fair Value, Recurring | Other | Level 3
Financial Assets:
Total available-for-sale investment securities	$ 0