Consolidated Statements of Cash Flow - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 137,011	$ 113,635
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan and lease losses	11,970	8,900
Depreciation, amortization and accretion, net	27,557	30,220
Deferred income taxes	5,416	4,425
Stock-based compensation	3,326	2,994
Other gains	(1,088)	(133)
Originations of loans held for sale	(10,921)
Proceeds from sales of loans held for sale	8,944
Net gains on sales of loans held for sale	(66)	(13)
Change in assets and liabilities:
Net decrease in other assets	11,977	13,487
Net decrease in other liabilities	(14,080)	(14,619)
Net cash provided by operating activities	180,046	158,896
Available-for-sale securities:
Proceeds from maturities and principal repayments	425,182	412,621
Purchases	(130,252)	(438,348)
Other investments:
Proceeds from sales	7,918	11,463
Purchases	(28,153)	(9,651)
Loans:
Net increase in loans and leases resulting from originations and principal repayments	(364,620)	(539,237)
Proceeds from sales of loans originated for investment	562	672
Purchases of loans		(8,000)
Proceeds from bank-owned life insurance		3,987
Purchases of premises, equipment and software	(9,752)	(4,019)
Proceeds from sales of premises and equipment		27
Purchases of mortgage servicing rights	(6,444)
Proceeds from sales of other real estate owned	332	635
Other	(1,325)	(1,046)
Net cash used in investing activities	(106,552)	(570,896)
Cash flows from financing activities
Net (decrease) increase in deposits	(216,584)	657,730
Net decrease in short-term borrowings		(9,151)
Proceeds from long-term debt	200,000
Dividends paid	(66,296)	(61,400)
Proceeds from employee stock purchase plan	342	528
Common stock repurchased	(81,800)
Net cash (used in) provided by financing activities	(164,338)	587,707
Net (decrease) increase in cash and cash equivalents	(90,844)	175,707
Cash and cash equivalents at beginning of period	1,034,644	1,052,058
Cash and cash equivalents at end of period	943,800	1,227,765
Supplemental disclosures
Interest paid	32,764	15,154
Income taxes paid, net of income tax refunds	1,548	31,091
Noncash investing and financing activities:
Transfers from loans and leases to other real estate owned	$ 64	524
Transfers from loans and leases to loans held for sale		$ 659