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	141,647				141,647
Other comprehensive income/(loss)	21,373					21,373
Cash dividends declared	(42,805)				(42,805)
Preferred stock dividends	(7,020)				(7,020)
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit (in shares)			144,670
Common stock issued under incentive plans, net of shares surrendered in payment	232		$ 145	87
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	11,229			11,229
Ending balance (in shares) at Sep. 30, 2016		13,750	41,081,701
Ending balance at Sep. 30, 2016	2,667,110	$ 132,097	$ 41,082	1,797,835	676,308	19,788
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, including tax benefit (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)