Fair Value Measurement and Fair Value of Financial Instruments (Financial Assets and Liabilities Measurement on Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	$ 2,640,158	$ 2,741,847
Derivative
Derivative assets - Fair value	135,782	107,816
Derivative asset, after netting	95,744	62,670
Derivative liabilities - Fair value	109,587	118,305
Derivative liability, after netting	53,485	79,903
U.S. Treasury securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	520,440	564,815
U.S. government agency and U.S. government sponsored enterprise debt securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	182,536	217,173
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	426,291	408,603
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	886,825	946,693
Municipal securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	76,004	82,020
Non-agency commercial mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	42,299	26,052
Non-agency residential mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	9,455	9,931
Corporate debt securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	11,094	10,869
Foreign bonds
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	472,669	463,048
Asset-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	12,545	12,643
Fair Value, Measurements, Recurring
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	2,640,158	2,741,847
Equity securities with readily determinable fair value	30,937	31,209
Total investments in tax credit and other investments	30,937	31,209
Derivative
Derivative assets - Fair value	135,782	107,816
Derivative asset netting adjustments	(40,038)	(45,146)
Derivative asset, after netting	95,744	62,670
Derivative liabilities - Fair value	109,587	118,305
Derivative liability netting adjustment	(56,102)	(38,402)
Derivative liability, after netting	53,485	79,903
Fair Value, Measurements, Recurring | Interest rate contracts
Derivative
Derivative assets - Fair value	96,256	69,818
Derivative liabilities - Fair value	76,572	75,133
Fair Value, Measurements, Recurring | Foreign exchange contracts
Derivative
Derivative assets - Fair value	30,085	21,624
Derivative liabilities - Fair value	24,918	19,940
Fair Value, Measurements, Recurring | Credit contracts
Derivative
Derivative assets - Fair value	1	1
Derivative liabilities - Fair value	81	164
Fair Value, Measurements, Recurring | Equity contracts
Derivative
Derivative assets - Fair value	2,201	1,951
Fair Value, Measurements, Recurring | Commodity contracts
Derivative
Derivative assets - Fair value	7,239	14,422
Derivative liabilities - Fair value	8,016	23,068
Fair Value, Measurements, Recurring | U.S. Treasury securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	520,440	564,815
Fair Value, Measurements, Recurring | U.S. government agency and U.S. government sponsored enterprise debt securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	182,536	217,173
Fair Value, Measurements, Recurring | 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	426,291	408,603
Fair Value, Measurements, Recurring | 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	886,825	946,693
Fair Value, Measurements, Recurring | Municipal securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	76,004	82,020
Fair Value, Measurements, Recurring | Non-agency commercial mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	42,299	26,052
Fair Value, Measurements, Recurring | Non-agency residential mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	9,455	9,931
Fair Value, Measurements, Recurring | Corporate debt securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	11,094	10,869
Fair Value, Measurements, Recurring | Foreign bonds
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	472,669	463,048
Fair Value, Measurements, Recurring | Asset-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	12,545	12,643
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	520,440	564,815
Equity securities with readily determinable fair value	21,051	20,678
Total investments in tax credit and other investments	21,051	20,678
Derivative
Derivative assets - Fair value	0	0
Derivative asset netting adjustments	0	0
Derivative asset, after netting	0	0
Derivative liabilities - Fair value	0	0
Derivative liability netting adjustment	0	0
Derivative liability, after netting	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	0
Derivative liabilities - Fair value	0	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	520,440	564,815
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 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 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) | Corporate 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) | Foreign bonds
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 securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	2,119,718	2,177,032
Equity securities with readily determinable fair value	9,886	10,531
Total investments in tax credit and other investments	9,886	10,531
Derivative
Derivative assets - Fair value	135,340	107,143
Derivative asset netting adjustments	(40,038)	(45,146)
Derivative asset, after netting	95,302	61,997
Derivative liabilities - Fair value	109,587	118,305
Derivative liability netting adjustment	(56,102)	(38,402)
Derivative liability, after netting	53,485	79,903
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate contracts
Derivative
Derivative assets - Fair value	96,256	69,818
Derivative liabilities - Fair value	76,572	75,133
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign exchange contracts
Derivative
Derivative assets - Fair value	30,085	21,624
Derivative liabilities - Fair value	24,918	19,940
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Credit contracts
Derivative
Derivative assets - Fair value	1	1
Derivative liabilities - Fair value	81	164
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Equity contracts
Derivative
Derivative assets - Fair value	1,759	1,278
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Commodity contracts
Derivative
Derivative assets - Fair value	7,239	14,422
Derivative liabilities - Fair value	8,016	23,068
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	182,536	217,173
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	426,291	408,603
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	886,825	946,693
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Municipal securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	76,004	82,020
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Non-agency commercial mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	42,299	26,052
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Non-agency residential mortgage-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	9,455	9,931
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	11,094	10,869
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign bonds
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	472,669	463,048
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Asset-backed securities
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	12,545	12,643
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Investment securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Equity securities with readily determinable fair value	0	0
Total investments in tax credit and other investments	0	0
Derivative
Derivative assets - Fair value	442	673
Derivative asset netting adjustments	0	0
Derivative asset, after netting	442	673
Derivative liabilities - Fair value	0	0
Derivative liability netting adjustment	0	0
Derivative liability, after netting	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	442	673
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Commodity contracts
Derivative
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	0	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 securities available-for-sale
Available-for-sale debt securities, Fair Value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Non-agency 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) | Corporate 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) | Foreign bonds
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 securities available-for-sale
Available-for-sale debt securities, Fair Value	$ 0	$ 0