Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands		Total	Stock options	Common stock	Common stock Stock options	Additional paid-in capital	Additional paid-in capital Stock options	Retained earnings	Accumulated other comprehensive income (loss)
Changes in Stockholders' Equity
Cumulative effect adjustment of change in accounting policy, net of tax impact	[1]	$ 1,339						$ 1,680	$ (341)
Beginning balance at Dec. 31, 2017		2,668,749		$ 71,207		$ 2,203,637		419,403	(25,498)
Changes in Stockholders' Equity
Comprehensive income		56,381						71,596	(15,215)
Cash dividends		(20,075)						(20,075)
Net shares issued under share-based compensation plans			$ (3,343)		$ 143		$ (3,486)
Share-based compensation expense		1,652		0		1,652
Ending balance at Mar. 31, 2018		2,704,703		71,350		2,201,803		472,604	(41,054)
Beginning balance at Dec. 31, 2018		2,836,260		71,460		2,209,761		616,149	(61,110)
Changes in Stockholders' Equity
Comprehensive income		85,545						62,942	22,603
Cash dividends		(24,486)						(24,486)
Net shares issued under share-based compensation plans			$ (2,183)		$ 91		$ (2,274)
Share-based compensation expense		2,373		0		2,373
Ending balance at Mar. 31, 2019		$ 2,897,509		$ 71,551		$ 2,209,860		$ 654,605	$ (38,507)

[1] Refer to Note 1, Basis of Presentation and Significant Accounting Policies, Note 6, Other Real Estate Owned and Repossessed Assets and Note 20, Accumulated Other Comprehensive Loss for further details on changes in accounting policy.