Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2017		13,750	53,872,272
Beginning balance at Dec. 31, 2017	$ 3,696,791	$ 132,097	$ 53,872	$ 2,787,484	$ 769,226	$ (45,888)
Increase (Decrease) in Shareholders' Equity
Net income	63,621				63,621
Other comprehensive income (loss)	(50,795)					(50,795)
Cash dividends declared	(21,579)				(21,579)
Preferred stock dividends	(3,598)				(3,598)
Common stock issued under incentive plans, net of shares surrendered in payment (in shares)			118,796
Common stock issued under incentive plans, net of shares surrendered in payment	(2,581)		$ 119	(2,700)
Common stock issued for acquisitions (in shares)			2,787,773
Common stock issued for acquisitions	214,659		$ 2,788	211,871
Share-based compensation expense	4,734			4,734
Ending balance (in shares) at Mar. 31, 2018		13,750	56,778,841
Ending balance at Mar. 31, 2018	3,900,907	$ 132,097	$ 56,779	3,001,389	807,325	(96,683)
Beginning balance (in shares) at Dec. 31, 2018		13,750	54,796,231
Beginning balance at Dec. 31, 2018	4,056,277	$ 132,097	$ 54,796	2,869,416	1,042,718	(42,750)
Increase (Decrease) in Shareholders' Equity
Net income	100,131				100,131
Other comprehensive income (loss)	39,450					39,450
Cash dividends declared	(23,457)				(23,457)
Preferred stock dividends	(3,598)				(3,598)
Common stock issued under incentive plans, net of shares surrendered in payment (in shares)			142,954
Common stock issued under incentive plans, net of shares surrendered in payment	(4,445)		$ 143	(4,588)
Common stock repurchases (in shares)			(387,921)
Common stock repurchases	(29,946)		$ (388)	(29,558)
Share-based compensation expense	5,572			5,572
Ending balance (in shares) at Mar. 31, 2019		13,750	54,551,264
Ending balance at Mar. 31, 2019	$ 4,141,831	$ 132,097	$ 54,551	$ 2,840,842	$ 1,117,641	$ (3,300)