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, 2016		13,750	44,795,386
Beginning balance at Dec. 31, 2016	$ 2,939,694	$ 132,097	$ 44,795	$ 2,084,446	$ 704,391	$ (26,035)
Increase (Decrease) in Shareholders' Equity
Net income	132,135				132,135
Other comprehensive income/(loss)	13,086					13,086
Cash dividends declared	(56,683)				(56,683)
Preferred stock dividends	(8,146)				(8,146)
Common stock issued under incentive plans, net of shares surrendered in payment (in shares)			358,560
Common stock issued under incentive plans, net of shares surrendered in payment	(1,605)		$ 359	(1,964)
Shares issued (in shares)			8,710,304
Common stock issued	696,794		$ 8,710	688,084
Share-based compensation cost	11,499			11,499
Ending balance (in shares) at Sep. 30, 2017		13,750	53,864,250
Ending balance at Sep. 30, 2017	3,726,774	$ 132,097	$ 53,864	2,782,065	771,697	(12,949)
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	240,210				240,210
Other comprehensive income/(loss)	(87,476)					(87,476)
Cash dividends declared	(64,288)				(64,288)
Preferred stock dividends	(8,146)				(8,146)
Common stock issued under incentive plans, net of shares surrendered in payment (in shares)			109,983
Common stock issued under incentive plans, net of shares surrendered in payment	(3,142)		$ 110	(3,252)
Common stock issued for acquisitions (in shares)			2,787,773
Common stock issued for acquisitions	214,659		$ 2,788	211,871
Common stock repurchases (in shares)			(763,210)
Common stock repurchases	(61,046)		$ (763)	(60,283)
Share-based compensation cost	15,144			15,144
Ending balance (in shares) at Sep. 30, 2018		13,750	56,006,818
Ending balance at Sep. 30, 2018	$ 3,942,361	$ 132,097	$ 56,007	$ 2,950,964	$ 936,657	$ (133,364)