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	102,491				102,491
Other comprehensive income/(loss)	12,109					12,109
Cash dividends declared	(36,752)				(36,752)
Preferred stock dividends	(4,548)				(4,548)
Common stock issued under incentive plans, net of shares surrendered in payment (in shares)			119,494
Common stock issued under incentive plans, net of shares surrendered in payment	(2,057)		$ 120	(2,177)
Shares issued (in shares)			6,100,000
Common stock issued	485,194		$ 6,100	479,094
Share-based compensation cost	7,111			7,111
Ending balance (in shares) at Jun. 30, 2017		13,750	51,014,880
Ending balance at Jun. 30, 2017	3,503,242	$ 132,097	$ 51,015	2,568,474	765,582	(13,926)
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	138,745				138,745
Other comprehensive income/(loss)	(66,096)					(66,096)
Cash dividends declared	(43,006)				(43,006)
Preferred stock dividends	(4,547)				(4,547)
Common stock issued under incentive plans, net of shares surrendered in payment (in shares)			130,342
Common stock issued under incentive plans, net of shares surrendered in payment	(2,102)		$ 130	(2,232)
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)			(400,000)
Common stock repurchases	(30,670)		$ (400)	(30,270)
Share-based compensation cost	9,980			9,980
Ending balance (in shares) at Jun. 30, 2018		13,750	56,390,387
Ending balance at Jun. 30, 2018	$ 3,913,409	$ 132,097	$ 56,390	$ 2,976,833	$ 860,073	$ (111,984)