Fair Value Measurements (Detail 5) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Financial Assets:
Cash and due from banks	$ 433,629	$ 336,470
Due from banks - interest-bearing	704,258	119,981
Securities purchased under resale agreements	200,104	200,108
Securities held-to-maturity	3,460,942	3,484,647
Loans and leases, net of allowance	21,612,406	20,027,057
Covered loans, net of allowance	425,958	502,371
FDIC indemnification asset	34,799	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	433,600	336,500
Due from banks - interest-bearing	704,300	120,000
Financial Liabilities:
Short-term borrowings		320,000
Significant Other Observable Inputs Level 2
Financial Assets:
Securities purchased under resale agreements	201,300	201,100
Securities held-to-maturity	3,460,900	3,484,600
Investment in FHLB and FRB stock	50,600	58,400
Financial Liabilities:
Deposits	28,917,800	27,435,100
Long-term debt	606,800	605,300
Significant Unobservable Inputs Level 3
Financial Assets:
Loans and leases, net of allowance	22,102,900	20,576,900
Covered loans, net of allowance	471,000	549,100
FDIC indemnification asset	27,800	40,200
Financial Liabilities:
Deposits	564,400	674,500
Short-term borrowings	6,300	2,900
Long-term debt	101,200	99,000
Carrying Amount
Financial Assets:
Cash and due from banks	433,600	336,500
Due from banks - interest-bearing	704,300	120,000
Securities purchased under resale agreements	200,000	200,000
Securities held-to-maturity	3,422,200	3,427,000
Loans and leases, net of allowance	21,612,400	20,027,100
Covered loans, net of allowance	426,000	502,400
FDIC indemnification asset	34,800	50,500
Investment in FHLB and FRB stock	50,600	58,400
Financial Liabilities:
Deposits	29,481,200	28,108,100
Short-term borrowings	6,300	322,900
Long-term debt	640,600	638,600
Fair Value
Financial Assets:
Cash and due from banks	433,600	336,500
Due from banks - interest-bearing	704,300	120,000
Securities purchased under resale agreements	201,300	201,100
Securities held-to-maturity	3,460,900	3,484,600
Loans and leases, net of allowance	22,102,900	20,576,900
Covered loans, net of allowance	471,000	549,100
FDIC indemnification asset	27,800	40,200
Investment in FHLB and FRB stock	50,600	58,400
Financial Liabilities:
Deposits	29,482,200	28,109,600
Short-term borrowings	6,300	322,900
Long-term debt	$ 708,000	$ 704,300