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	50,473				50,473
Other comprehensive income/(loss)	4,614					4,614
Cash dividends declared	(18,271)				(18,271)
Preferred stock dividends	(3,599)				(3,599)
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit (in shares)			74,522
Common stock issued under incentive plans, net of shares surrendered in payment	(3,851)		$ 75	(3,926)
Shares issued (in shares)			6,100,000
Common stock issued			$ 6,100	479,094
Preferred Stock Issued During Period, Value, New Issues	485,194
Share-based compensation cost	3,721			3,721
Ending balance (in shares) at Mar. 31, 2017		13,750	50,969,908
Ending balance at Mar. 31, 2017	3,457,975	$ 132,097	$ 50,970	2,563,335	732,994	(21,421)
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, including tax benefit (in shares)			118,796
Common stock issued under incentive plans, net of shares surrendered in payment	(2,581)		$ 119	(2,700)
Stock Issued During Period, Shares, Acquisitions			2,787,773
Stock Issued During Period, Value, Acquisitions	214,659		$ 2,788	211,871
Share-based compensation cost	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)