Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	$ 49,480	$ 43,380
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	3,970	4,800
Depreciation and amortization of premises and equipment	7,329	7,032
Amortization of tax credit investments	8,364	9,128
Net amortization of investment securities premiums	2,517	2,416
Investment securities gains, net	(19)	(1,106)
Gain on sales of mortgage loans held for sale	(2,645)	(3,074)
Proceeds from sales of mortgage loans held for sale	170,693	115,417
Originations of mortgage loans held for sale	(159,968)	(108,429)
Amortization of issuance costs on long-term debt	194	168
Stock-based compensation	1,510	734
Increase in accrued interest receivable	(150)	(61)
Increase in other assets	(6,923)	(4,514)
Increase in accrued interest payable	364	2,874
(Decrease) increase in other liabilities	(2,890)	1,039
Total adjustments	22,346	26,424
Net cash provided by operating activities	71,826	69,804
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sales of securities available for sale	1,444	8,735
Proceeds from principal repayments and maturities of securities available for sale	78,150	98,024
Purchase of securities available for sale	(161,944)	(49,430)
Decrease (increase) in short-term investments	86,760	(59,135)
Net decrease (increase) in loans	67,928	(267,383)
Net change in tax credit investments	(14,840)	(5,397)
Net change in tax credit investments	20,783	5,283
Net cash provided by (used in) investing activities	36,715	(279,869)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net (decrease) increase in demand and savings deposits	(278,626)	112,348
Net decrease in time deposits	(41,803)	(34,868)
Increase (decrease) in short-term borrowings	320,328	(88,000)
Additions to long-term debt	0	223,375
Repayments of long-term debt	(100,041)	(15,037)
Net proceeds from issuance of common stock	2,790	4,731
Dividends paid	(19,329)	(17,403)
Net cash (used in) provided by financing activities	(116,681)	185,146
Net Decrease in Cash and Due From Banks	(8,140)	(24,919)
Cash and Due From Banks at Beginning of Period	108,291	118,763
Cash and Due From Banks at End of Period	100,151	93,844
Cash paid during the period for:
Interest	26,005	18,034
Income taxes	$ 154	$ 116