UNAUDITED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated OCI
Balance at Dec. 31, 2017	$ 1,359,056	$ 836	$ 1,037,040		$ 340,213	$ (19,033)
Equity-based compensation cost	453		453
Net income	38,825				38,825
Cash dividends declared	(10,453)				(10,453)
Cumulative effect of adoption of new accounting principle	1,000				1,000
Other comprehensive income (loss)	(31,778)					(31,778)
Balance at Mar. 31, 2018	1,357,103	836	1,037,493		369,585	(50,811)
Balance at Dec. 31, 2018	1,438,274	836	1,041,000	$ (22,010)	461,360	(42,912)
Equity-based compensation cost	1,188		1,188
Net income	58,201				58,201
Cash dividends declared	(22,727)				(22,727)
Dividend equivalents on restricted stock units (Note 20)	(125)				(125)
Purchase of treasury stock - at cost	(58,830)			(58,830)
Issuance of 49,232,008 common shares for State Bank acquisition, net of issuance costs (Note 2)	826,113	492	825,621
Value of stock warrants assumed from State Bank acquisition	251		251
Common stock issuance costs	(295)		(295)
Issuance of 34,587 common shares for restricted stock unit vesting (Note 20)		1	(1)
Issuance of treasury stock shares for exercise of stock warrant			(7)	7
Other comprehensive income (loss)	60,773					60,773
Balance at Mar. 31, 2019	$ 2,302,823	$ 1,329	$ 1,867,757	$ (80,833)	$ 496,709	$ 17,861