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	42,769				42,769
Other comprehensive income/(loss)	21,193					21,193
Cash dividends declared	(14,019)				(14,019)
Preferred stock dividends	(2,576)				(2,576)
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit (in shares)			92,323
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit	(2,163)		$ 92	(2,255)
Preferred stock dividends				0
Share-based compensation cost	3,870			3,870
Ending balance (in shares) at Mar. 31, 2016		8,000	41,231,860
Ending balance at Mar. 31, 2016	2,547,909	$ 76,812	$ 41,232	1,799,597	610,660	19,608
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, including tax benefit	(3,851)		$ 75	(3,926)
Shares issued (in shares)			6,100,000
Common stock issued	485,194		$ 6,100	479,094
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)
Stock Repurchase Program, Remaining Authorized Repurchase Amount	747,494