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, 2015		8,000	41,139,537
Beginning balance at Dec. 31, 2015	$ 2,498,835	$ 76,812	$ 41,140	$ 1,797,982	$ 584,486	$ (1,585)
Increase (Decrease) in Shareholders' Equity
Net income	93,579				93,579
Other comprehensive income/(loss)	27,569					27,569
Cash dividends declared	(28,016)				(28,016)
Preferred stock dividends	(3,430)				(3,430)
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit (in shares)			101,802
Common stock issued under incentive plans, net of shares surrendered in payment	(2,262)		$ 102	(2,364)
Preferred stock issued (in shares)		5,750
Preferred stock issued	55,285	$ 55,285
Common stock repurchases (in shares)			(202,506)
Common stock repurchases	(11,666)		$ (203)	(11,463)
Share-based compensation cost	7,702			7,702
Ending balance (in shares) at Jun. 30, 2016		13,750	41,038,833
Ending balance at Jun. 30, 2016	2,637,596	$ 132,097	$ 41,039	1,791,857	646,619	25,984
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, including tax benefit (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)