Fair Value Measurements (Carrying Amounts and Estimated Fair Values) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets:
Held-to-maturity	$ 608,531	$ 512,705
Liabilities:
Short-term borrowings	825,000	100,000
Long-term borrowings	597,847	242,391
Nonrecurring
Liabilities:
Assets measured at fair value on a nonrecurring basis	63,572	45,133
Nonrecurring | Impaired originated loans
Liabilities:
Assets measured at fair value on a nonrecurring basis		42,065
Level 1 | Nonrecurring
Liabilities:
Assets measured at fair value on a nonrecurring basis	0	0
Level 1 | Nonrecurring | Impaired originated loans
Liabilities:
Assets measured at fair value on a nonrecurring basis	0	0
Level 2 | Nonrecurring
Liabilities:
Assets measured at fair value on a nonrecurring basis	0	0
Level 2 | Nonrecurring | Impaired originated loans
Liabilities:
Assets measured at fair value on a nonrecurring basis	0	0
Level 3 | Nonrecurring
Liabilities:
Assets measured at fair value on a nonrecurring basis	63,572	45,133
Level 3 | Nonrecurring | Impaired originated loans
Liabilities:
Assets measured at fair value on a nonrecurring basis	62,184	42,065
Carrying Amount
Assets:
Nonmarketable equity securities	97,350	36,907
Carrying Amount | Level 1
Assets:
Cash and cash equivalents	474,402	238,789
Carrying Amount | Level 2
Assets:
Held-to-maturity	622,927	509,471
Interest receivable	42,235	21,953
Liabilities:
Deposits without defined maturities	9,862,755	5,809,355
Time deposits	3,010,367	1,647,412
Total deposits	12,873,122	7,456,767
Interest payable	5,415	1,578
Securities sold under agreements to repurchase with customers	343,047	297,199
Short-term borrowings	825,000	100,000
Long-term borrowings	597,847	242,391
Carrying Amount | Level 3
Assets:
Held-to-maturity	500	500
Net loans	12,912,511	7,197,819
Fair Value
Assets:
Nonmarketable equity securities	97,350	36,907
Fair Value | Level 1
Assets:
Cash and cash equivalents	474,402	238,789
Fair Value | Level 2
Assets:
Held-to-maturity	608,221	512,405
Interest receivable	42,235	21,953
Liabilities:
Deposits without defined maturities	9,862,755	5,809,355
Time deposits	3,010,048	1,647,412
Total deposits	12,872,803	7,456,767
Interest payable	5,415	1,578
Securities sold under agreements to repurchase with customers	343,047	297,199
Short-term borrowings	825,000	100,000
Long-term borrowings	591,227	242,391
Fair Value | Level 3
Assets:
Held-to-maturity	310	7,090
Net loans	$ 13,069,315	$ 7,201,994