Fair Value Measurements (Detail 5) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financial Assets:
Cash and due from banks	$ 434,087	$ 336,470
Due from banks - interest-bearing	1,424,109	119,981
Securities purchased under resale agreements	200,302	200,108
Securities held-to-maturity	3,598,902	3,484,647
Loans and leases, net of allowance	22,219,427	20,027,057
Acquired impaired loans, net of allowance	393,879	502,371
FDIC indemnification asset	28,164	50,511
Investment in FHLB and FRB stock	50,600	58,400
Quoted Prices in Active Markets Level 1
Financial Assets:
Cash and due from banks	434,100	336,500
Due from banks - interest-bearing	1,424,100	120,000
Financial Liabilities:
Short-term borrowings		320,000
Significant Other Observable Inputs Level 2
Financial Assets:
Securities purchased under resale agreements	201,000	201,100
Securities held-to-maturity	3,598,900	3,484,600
Investment in FHLB and FRB stock	50,600	58,400
Financial Liabilities:
Deposits	30,601,300	27,435,100
Long-term debt	614,700	605,300
Significant Unobservable Inputs Level 3
Financial Assets:
Loans and leases, net of allowance	22,772,000	20,576,900
Acquired impaired loans, net of allowance	443,000	549,100
FDIC indemnification asset	22,400	40,200
Financial Liabilities:
Deposits	573,000	674,500
Short-term borrowings	6,500	2,900
Long-term debt	111,200	99,000
Carrying Amount
Financial Assets:
Cash and due from banks	434,100	336,500
Due from banks - interest-bearing	1,424,100	120,000
Securities purchased under resale agreements	200,000	200,000
Securities held-to-maturity	3,506,500	3,427,000
Loans and leases, net of allowance	22,219,400	20,027,100
Acquired impaired loans, net of allowance	393,900	502,400
FDIC indemnification asset	28,200	50,500
Investment in FHLB and FRB stock	50,600	58,400
Financial Liabilities:
Deposits	31,173,400	28,108,100
Short-term borrowings	6,500	322,900
Long-term debt	650,100	638,600
Fair Value
Financial Assets:
Cash and due from banks	434,100	336,500
Due from banks - interest-bearing	1,424,100	120,000
Securities purchased under resale agreements	201,000	201,100
Securities held-to-maturity	3,598,900	3,484,600
Loans and leases, net of allowance	22,772,000	20,576,900
Acquired impaired loans, net of allowance	443,000	549,100
FDIC indemnification asset	22,400	40,200
Investment in FHLB and FRB stock	50,600	58,400
Financial Liabilities:
Deposits	31,174,300	28,109,600
Short-term borrowings	6,500	322,900
Long-term debt	$ 725,900	$ 704,300