Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 142,357	$ 137,011
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan and lease losses	9,550	11,970
Depreciation, amortization and accretion, net	32,959	27,557
Deferred income taxes	15,724	5,416
Stock-based compensation	3,551	3,326
Other gains	(8)	(1,088)
Originations of loans held for sale	(4,091)	(10,921)
Proceeds from sales of loans held for sale	4,343	8,944
Net gains on sales of loans held for sale	(35)	(66)
Net losses on investment securities	2,592
Change in assets and liabilities:
Net decrease in other assets	1,145	11,977
Net decrease in other liabilities	(63,844)	(14,080)
Net cash provided by operating activities	144,243	180,046
Available-for-sale securities:
Proceeds from maturities and principal repayments	322,954	425,182
Proceeds from sales	905,605
Purchases	(999,491)	(130,252)
Other investments:
Proceeds from sales	4,854	7,918
Purchases	(12,693)	(28,153)
Loans:
Net decrease (increase) in loans and leases resulting from originations and principal repayments	21,111	(364,620)
Proceeds from sales of loans originated for investment		562
Purchases of loans	(222,816)
Proceeds from bank-owned life insurance	2,557
Purchases of premises, equipment and software	(16,269)	(9,752)
Purchases of mortgage servicing rights		(6,444)
Proceeds from sales of other real estate owned	759	332
Other	(1,429)	(1,325)
Net cash provided by (used in) investing activities	5,142	(106,552)
Cash flows from financing activities
Net decrease in deposits	(357,990)	(216,584)
Proceeds from long-term borrowings		200,000
Dividends paid	(69,984)	(66,296)
Stock tendered for payment of withholding taxes	(1,533)
Proceeds from employee stock purchase plan		342
Common stock repurchased	(40,000)	(81,800)
Net cash used in financing activities	(469,507)	(164,338)
Net decrease in cash and cash equivalents	(320,122)	(90,844)
Cash and cash equivalents at beginning of period	1,003,637	1,034,644
Cash and cash equivalents at end of period	683,515	943,800
Supplemental disclosures
Interest paid	51,421	32,764
Income taxes paid, net of income tax refunds	41,593	1,548
Noncash investing and financing activities:
Transfers from loans and leases to other real estate owned		$ 64
Operating lease right-of-use assets obtained in exchange for new lease obligations	$ 680