Earnings per Share Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income									$ 127,587	$ 107,663	$ 72,081
Preferred dividends									0	0	(3,656)
Excess of fair value over book value of preferred shares redeemed									0	0	(2,257)
Net Income Available to Common Stockholders	$ 41,780	$ 37,838	$ 30,246	$ 17,723	$ 32,407	$ 29,282	$ 27,911	$ 18,063	127,587	107,663	66,168
Diluted income available to common shareholders									$ 127,587	$ 108,070	$ 69,387
Basic Weighted Average Shares Outstanding	28,297	27,981	27,599	27,498	27,774	28,469	28,571	28,124	27,846	28,234	25,769
Stock option awards									412	295	342
Deferred Compensation Awards									217	219	221
Diluted Weighted Average Shares Outstanding	29,049	28,598	28,090	27,970	28,181	28,906	29,101	30,544	28,475	29,178	30,688
Earnings Per Share, Basic	$ 1.48	$ 1.35	$ 1.10	$ 0.64	$ 1.17	$ 1.03	$ 0.98	$ 0.64	$ 4.58	$ 3.81	$ 2.57
Earnings Per Share, Diluted	$ 1.44	$ 1.32	$ 1.08	$ 0.63	$ 1.15	$ 1.01	$ 0.96	$ 0.60	$ 4.48	$ 3.70	$ 2.26
Anti-dilutive stock equivalent awards not included in the calculation of diluted loss per share									1	381	23
2018 Convertible Senior Notes [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Interest on convertible senior subordinated notes									$ 0	$ 407	$ 2,113
Convertible senior subordinated notes potential shares									0	430	2,669
2017 Convertible Senior Notes [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Interest on convertible senior subordinated notes									$ 0	$ 0	$ 1,106
Convertible senior subordinated notes potential shares									0	0	1,687