Fair Value Measurements (Fair Value Assets And Liabilities Measured On Recurring Basis) (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets held at fair value	$ 3,060,771	$ 2,853,139
Derivative instruments	40,298	36,777
Contingent Liability	6,000
Total financial liabilities held at fair value	46,298	36,777
US Treasury Bill Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	924	525
Agency collateralized mortgage obligations (agency CMO) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	548,754	550,988
Agency mortgage-backed securities (agency MBS) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	1,065,109	1,028,518
Agency commercial mortgage-backed securities (agency CMBS) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	215,350	80,266
Non-agency commercial mortgage-backed securities (non-agency CMBS) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	579,266	553,393
Collateralized loan obligations (CLO) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	429,159	425,734
Single issuer trust preferred securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	37,170	38,245
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	106,321	110,301
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	2,578	5,903
Investments held In Rabbi Trust [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investments	5,372	5,901
Alternative investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investments	3,471	475
Derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	61,147	52,872
Mortgage banking derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	819	18
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets held at fair value	9,057	12,329
Derivative instruments	66	293
Total financial liabilities held at fair value	66	293
Fair Value, Inputs, Level 1 [Member] | US Treasury Bill Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	924	525
Fair Value, Inputs, Level 1 [Member] | Agency commercial mortgage-backed securities (agency CMBS) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Non-agency commercial mortgage-backed securities (non-agency CMBS) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	2,578	5,903
Fair Value, Inputs, Level 1 [Member] | Investments held In Rabbi Trust [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investments	5,372	5,901
Fair Value, Inputs, Level 1 [Member] | Alternative investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investments	0	0
Fair Value, Inputs, Level 1 [Member] | Derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	183	0
Fair Value, Inputs, Level 1 [Member] | Mortgage banking derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets held at fair value	3,042,912	2,840,335
Derivative instruments	40,232	36,484
Total financial liabilities held at fair value	40,232	36,484
Fair Value, Inputs, Level 2 [Member] | Agency collateralized mortgage obligations (agency CMO) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	548,754	550,988
Fair Value, Inputs, Level 2 [Member] | Agency mortgage-backed securities (agency MBS) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	1,065,109	1,028,518
Fair Value, Inputs, Level 2 [Member] | Agency commercial mortgage-backed securities (agency CMBS) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	215,350	80,266
Fair Value, Inputs, Level 2 [Member] | Non-agency commercial mortgage-backed securities (non-agency CMBS) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	579,266	553,393
Fair Value, Inputs, Level 2 [Member] | Collateralized loan obligations (CLO) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	429,159	425,734
Fair Value, Inputs, Level 2 [Member] | Single issuer trust preferred securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	37,170	38,245
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	106,321	110,301
Fair Value, Inputs, Level 2 [Member] | Alternative investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investments	0	0
Fair Value, Inputs, Level 2 [Member] | Derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	60,964	52,872
Fair Value, Inputs, Level 2 [Member] | Mortgage banking derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	819	18
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets held at fair value	8,802	475
Contingent Liability	6,000
Total financial liabilities held at fair value	6,000
Significant Unobservable Inputs (Level 3) [Member] | Agency commercial mortgage-backed securities (agency CMBS) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Non-agency commercial mortgage-backed securities (non-agency CMBS) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Alternative investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investments	3,471	475
Significant Unobservable Inputs (Level 3) [Member] | Derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0
Significant Unobservable Inputs (Level 3) [Member] | Mortgage banking derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Available-for-sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	2,984,631	2,793,873
Available-for-sale Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	3,502	6,428
Available-for-sale Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	2,981,129	$ 2,787,445
Contingent Asset [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investments	5,331
Contingent Asset [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investments	0
Contingent Asset [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investments	0
Contingent Asset [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative investments	$ 5,331