Consolidated Statements of Cash Flow - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 204,399	$ 171,998
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan and lease losses	16,430	13,400
Depreciation, amortization and accretion, net	41,893	46,273
Deferred income taxes	2,208	(6,348)
Stock-based compensation	4,884	4,171
Gains on sale of bank properties		(2,667)
Other gains	(897)	(133)
Originations of loans held for sale	(28,472)
Proceeds from sales of loans held for sale	28,614
Net gains on sales of loans held for sale	(148)
Change in assets and liabilities:
Net decrease (increase) in other assets	5,573	(935)
Net decrease in other liabilities	(8,973)	(11,257)
Net cash provided by operating activities	265,511	214,502
Available-for-sale securities:
Proceeds from maturities and principal repayments	637,538	644,854
Purchases	(130,251)	(864,049)
Other investments:
Proceeds from sales	10,333	13,318
Purchases	(45,432)	(11,484)
Loans:
Net increase in loans and leases resulting from originations and principal repayments	(171,306)	(626,262)
Proceeds from sales of loans originated for investment	562	1,775
Purchases of loans	(158,616)	(11,626)
Proceeds from bank-owned life insurance	1,154	4,226
Purchases of premises, equipment and software	(13,495)	(5,964)
Proceeds from sales of premises and equipment		3,857
Purchases of mortgage servicing rights	(6,444)
Proceeds from sales of other real estate owned	332	635
Other	(2,054)	(1,572)
Net cash provided by (used in) investing activities	122,321	(852,292)
Cash flows from financing activities
Net (decrease) increase in deposits	(922,849)	800,951
Net increase (decrease) in short-term borrowings	30,000	(9,151)
Proceeds from long-term borrowings	400,000
Repayment of long-term borrowings	(10)	(10)
Dividends paid	(98,666)	(92,101)
Stock tendered for payment of withholding taxes		(120)
Proceeds from employee stock purchase plan	342	528
Common stock repurchased	(131,800)
Net cash (used in) provided by financing activities	(722,983)	700,097
Net (decrease) increase in cash and cash equivalents	(335,151)	62,307
Cash and cash equivalents at beginning of period	1,034,644	1,052,058
Cash and cash equivalents at end of period	699,493	1,114,365
Supplemental disclosures
Interest paid	56,430	24,692
Income taxes paid, net of income tax refunds	29,204	87,240
Noncash investing and financing activities:
Transfers from loans and leases to other real estate owned	$ 143	759
Transfers from loans and leases to loans held for sale		$ 1,759