Fair Value Measurement and Fair Value of Financial Instruments (Financial Assets and Liabilities Measurement on Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	$ 2,676,510
Available-for-sale debt and equity securities, Fair Value		$ 3,016,752
Equity securities with readily determinable fair value		31,900
Derivative
Derivative assets - Fair value	99,103	66,146
Derivative liabilities - Fair value	133,702	74,935
U.S. Treasury securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	603,926	640,280
U.S. government agency and U.S. government sponsored enterprise debt securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	228,656	203,392
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	365,070	318,957
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	903,449	1,190,271
Municipal securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	72,824	99,982
Non-agency commercial mortgage-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	15,926
Non-agency residential mortgage-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	10,362	9,117
Corporate debt securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	10,942	37,003
Foreign bonds | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	452,843	486,408
Asset-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	12,512
Other securities
Investment securities available-for-sale
Other securities, Fair Value		31,342
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	603,926
Available-for-sale debt and equity securities, Fair Value		661,015
Equity securities with readily determinable fair value	20,373
Total investments in tax credit and other investments	20,373
Derivative
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate contracts
Derivative
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign exchange contracts
Derivative
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Credit contracts
Derivative
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity contracts
Derivative
Derivative assets - Fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Commodity contracts
Derivative
Derivative assets - Fair value	0
Derivative liabilities - Fair value	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	603,926	640,280
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. government agency and U.S. government sponsored enterprise debt securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Non-agency commercial mortgage-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Non-agency residential mortgage-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign bonds | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Asset-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other securities
Investment securities available-for-sale
Other securities, Fair Value		20,735
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	2,072,584
Available-for-sale debt and equity securities, Fair Value		2,355,737
Equity securities with readily determinable fair value	10,476
Total investments in tax credit and other investments	10,476
Derivative
Derivative assets - Fair value	98,431	65,467
Derivative liabilities - Fair value	133,702	74,935
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate contracts
Derivative
Derivative assets - Fair value	72,618	58,633
Derivative liabilities - Fair value	114,658	64,757
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign exchange contracts
Derivative
Derivative assets - Fair value	11,095	5,840
Derivative liabilities - Fair value	11,075	10,170
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Credit contracts
Derivative
Derivative assets - Fair value	1	1
Derivative liabilities - Fair value	57	8
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Equity contracts
Derivative
Derivative assets - Fair value	1,737	993
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Commodity contracts
Derivative
Derivative assets - Fair value	12,980
Derivative liabilities - Fair value	7,912
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. government agency and U.S. government sponsored enterprise debt securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	228,656	203,392
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	365,070	318,957
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	903,449	1,190,271
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Municipal securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	72,824	99,982
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Non-agency commercial mortgage-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	15,926
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Non-agency residential mortgage-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	10,362	9,117
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	10,942	37,003
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign bonds | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	452,843	486,408
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Asset-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	12,512
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other securities
Investment securities available-for-sale
Other securities, Fair Value		10,607
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0
Available-for-sale debt and equity securities, Fair Value		0
Equity securities with readily determinable fair value	0
Total investments in tax credit and other investments	0
Derivative
Derivative assets - Fair value	672	679
Derivative liabilities - Fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Interest rate contracts
Derivative
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Foreign exchange contracts
Derivative
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Credit contracts
Derivative
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Equity contracts
Derivative
Derivative assets - Fair value	672	679
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Commodity contracts
Derivative
Derivative assets - Fair value	0
Derivative liabilities - Fair value	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. government agency and U.S. government sponsored enterprise debt securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Municipal securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Non-agency commercial mortgage-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Non-agency residential mortgage-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate debt securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Foreign bonds | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Asset-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Other securities
Investment securities available-for-sale
Other securities, Fair Value		0
Fair Value, Measurements, Recurring | Fair Value Measurements
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	2,676,510
Available-for-sale debt and equity securities, Fair Value		3,016,752
Equity securities with readily determinable fair value	30,849
Total investments in tax credit and other investments	30,849
Derivative
Derivative assets - Fair value	99,103	66,146
Derivative liabilities - Fair value	133,702	74,935
Fair Value, Measurements, Recurring | Fair Value Measurements | Interest rate contracts
Derivative
Derivative assets - Fair value	72,618	58,633
Derivative liabilities - Fair value	114,658	64,757
Fair Value, Measurements, Recurring | Fair Value Measurements | Foreign exchange contracts
Derivative
Derivative assets - Fair value	11,095	5,840
Derivative liabilities - Fair value	11,075	10,170
Fair Value, Measurements, Recurring | Fair Value Measurements | Credit contracts
Derivative
Derivative assets - Fair value	1	1
Derivative liabilities - Fair value	57	8
Fair Value, Measurements, Recurring | Fair Value Measurements | Equity contracts
Derivative
Derivative assets - Fair value	2,409	1,672
Fair Value, Measurements, Recurring | Fair Value Measurements | Commodity contracts
Derivative
Derivative assets - Fair value	12,980
Derivative liabilities - Fair value	7,912
Fair Value, Measurements, Recurring | Fair Value Measurements | U.S. Treasury securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	603,926	640,280
Fair Value, Measurements, Recurring | Fair Value Measurements | U.S. government agency and U.S. government sponsored enterprise debt securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	228,656	203,392
Fair Value, Measurements, Recurring | Fair Value Measurements | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	365,070	318,957
Fair Value, Measurements, Recurring | Fair Value Measurements | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	903,449	1,190,271
Fair Value, Measurements, Recurring | Fair Value Measurements | Municipal securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	72,824	99,982
Fair Value, Measurements, Recurring | Fair Value Measurements | Non-agency commercial mortgage-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	15,926
Fair Value, Measurements, Recurring | Fair Value Measurements | Non-agency residential mortgage-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	10,362	9,117
Fair Value, Measurements, Recurring | Fair Value Measurements | Corporate debt securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	10,942	37,003
Fair Value, Measurements, Recurring | Fair Value Measurements | Foreign bonds | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	452,843	486,408
Fair Value, Measurements, Recurring | Fair Value Measurements | Asset-backed securities | Investment grade
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	$ 12,512
Fair Value, Measurements, Recurring | Fair Value Measurements | Other securities
Investment securities available-for-sale
Other securities, Fair Value		$ 31,342