Consolidated Statements of Changes in Shareholders' Equity $ in Thousands	USD ($)
Total shareholders’ equity at beginning of period at Dec. 31, 2016	$ 3,002,528
Cumulative effect of accounting change at Dec. 31, 2016	0
Total shareholders' equity at beginning of period, as adjusted at Dec. 31, 2016	3,002,528
Net income	84,941
Other comprehensive income (loss)	18,773
Stock option exercises/stock unit conversions (318,110 shares in 2018 and 442,054 shares in 2017)	24,747
Stock compensation expense recognized in earnings	3,103
Purchase of treasury stock (469 shares in 2017)	(42)
Cash dividends – preferred stock (approximately $0.34 per share in both 2018 and in 2017)	(2,016)
Cash dividends – common stock ($0.57 per share in 2018 and $0.54 per share in 2017)	(34,656)
Total shareholders’ equity at end of period at Mar. 31, 2017	3,097,378
Total shareholders’ equity at beginning of period at Dec. 31, 2017	3,297,863
Cumulative effect of accounting change at Dec. 31, 2017	(2,285)
Total shareholders' equity at beginning of period, as adjusted at Dec. 31, 2017	3,295,578
Net income	106,480
Other comprehensive income (loss)	(142,401)
Stock option exercises/stock unit conversions (318,110 shares in 2018 and 442,054 shares in 2017)	19,165
Stock compensation expense recognized in earnings	3,175
Purchase of treasury stock (469 shares in 2017)	0
Cash dividends – preferred stock (approximately $0.34 per share in both 2018 and in 2017)	(2,016)
Cash dividends – common stock ($0.57 per share in 2018 and $0.54 per share in 2017)	(36,551)
Total shareholders’ equity at end of period at Mar. 31, 2018	$ 3,243,430