Fair Value Measurements (Fair Value Assets And Liabilities Measured On Recurring Basis) (Detail) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Financial assets held at fair value:
Derivative Asset		$ 969	$ 0
Originated loans held for sale		32,855	60,260
Financial liabilities held at fair value:
Derivative liability		156	446
Alternative investments [Member]
Financial assets held at fair value:
Other assets		17,300
Fair Value, Measurements, Recurring [Member]
Financial assets held at fair value:
Total financial assets held at fair value		2,678,531	3,139,609
Financial liabilities held at fair value:
Derivative liability	[1]	20,023	45,189
Fair Value, Measurements, Recurring [Member] | Derivative instruments [Member]
Financial assets held at fair value:
Derivative Asset	[1]	42,250	77,637
Fair Value, Measurements, Recurring [Member] | Available-for-sale Investment Securities [Member]
Financial assets held at fair value:
Available for sale investment securities		2,591,162	2,991,091
Fair Value, Measurements, Recurring [Member] | US Treasury Bill Securities [Member]
Financial assets held at fair value:
Available for sale investment securities		3,596	734
Fair Value, Measurements, Recurring [Member] | Agency CMO [Member]
Financial assets held at fair value:
Available for sale investment securities		331,798	419,706
Fair Value, Measurements, Recurring [Member] | Agency MBS [Member]
Financial assets held at fair value:
Available for sale investment securities		912,977	954,349
Fair Value, Measurements, Recurring [Member] | Agency CMBS [Member]
Financial assets held at fair value:
Available for sale investment securities		584,960	573,272
Fair Value, Measurements, Recurring [Member] | CMBS [Member]
Financial assets held at fair value:
Available for sale investment securities		403,433	477,365
Fair Value, Measurements, Recurring [Member] | CLO [Member]
Financial assets held at fair value:
Available for sale investment securities		274,583	427,390
Fair Value, Measurements, Recurring [Member] | Single issuer trust preferred securities [Member]
Financial assets held at fair value:
Available for sale investment securities		30,937	28,633
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Financial assets held at fair value:
Available for sale investment securities		48,878	109,642
Fair Value, Measurements, Recurring [Member] | Investments held In Rabbi Trust [Member]
Financial assets held at fair value:
Other assets		5,278	5,119
Fair Value, Measurements, Recurring [Member] | Alternative investments [Member]
Financial assets held at fair value:
Other assets		6,986	5,502
Fair Value, Measurements, Recurring [Member] | Loan Origination Commitments [Member]
Financial assets held at fair value:
Originated loans held for sale		32,855	60,260
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member]
Financial assets held at fair value:
Total financial assets held at fair value		9,136	6,103
Financial liabilities held at fair value:
Derivative liability	[1]	562	120
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member] | Derivative instruments [Member]
Financial assets held at fair value:
Derivative Asset	[1]	262	250
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member] | Available-for-sale Investment Securities [Member]
Financial assets held at fair value:
Available for sale investment securities		3,596	734
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member] | US Treasury Bill Securities [Member]
Financial assets held at fair value:
Available for sale investment securities		3,596	734
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member] | Agency CMBS [Member]
Financial assets held at fair value:
Available for sale investment securities		0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member] | CMBS [Member]
Financial assets held at fair value:
Available for sale investment securities		0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member] | Investments held In Rabbi Trust [Member]
Financial assets held at fair value:
Other assets		5,278	5,119
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member] | Alternative investments [Member]
Financial assets held at fair value:
Other assets		0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets For Identical Assets (Level 1) [Member] | Loan Origination Commitments [Member]
Financial assets held at fair value:
Originated loans held for sale		0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets held at fair value:
Total financial assets held at fair value		2,662,409	3,128,004
Financial liabilities held at fair value:
Derivative liability	[1]	19,461	45,069
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Derivative instruments [Member]
Financial assets held at fair value:
Derivative Asset	[1]	41,988	77,387
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Available-for-sale Investment Securities [Member]
Financial assets held at fair value:
Available for sale investment securities		2,587,566	2,990,357
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Agency CMO [Member]
Financial assets held at fair value:
Available for sale investment securities		331,798	419,706
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Agency MBS [Member]
Financial assets held at fair value:
Available for sale investment securities		912,977	954,349
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Agency CMBS [Member]
Financial assets held at fair value:
Available for sale investment securities		584,960	573,272
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | CMBS [Member]
Financial assets held at fair value:
Available for sale investment securities		403,433	477,365
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | CLO [Member]
Financial assets held at fair value:
Available for sale investment securities		274,583	427,390
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Single issuer trust preferred securities [Member]
Financial assets held at fair value:
Available for sale investment securities		30,937	28,633
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate debt securities [Member]
Financial assets held at fair value:
Available for sale investment securities		48,878	109,642
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Alternative investments [Member]
Financial assets held at fair value:
Other assets		0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Loan Origination Commitments [Member]
Financial assets held at fair value:
Originated loans held for sale		32,855	60,260
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets held at fair value:
Total financial assets held at fair value		6,986	5,502
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Derivative instruments [Member]
Financial assets held at fair value:
Derivative Asset	[1]		0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Agency CMBS [Member]
Financial assets held at fair value:
Available for sale investment securities		0	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | CMBS [Member]
Financial assets held at fair value:
Available for sale investment securities		0	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Alternative investments [Member]
Financial assets held at fair value:
Other assets		$ 6,986	$ 5,502

[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 12: Derivative Financial Instruments.