Earnings per Share Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share Calculation [Line Items]
Net Income, Including Portion Attributable to Noncontrolling Interest	$ 29,282	$ 22,327	$ 75,256	$ 56,199
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Preferred Dividends	0	(1,218)	0	(3,656)
Excess of fair value over book value of preferred shares redeemed	0	(2,257)	0	(2,257)
Net income to common shareholders	29,282	18,852	75,256	50,286
Net Income Available to Common Stockholders, Diluted	$ 29,282	$ 19,706	$ 75,664	$ 52,978
Weighted Average Number of Shares Outstanding, Basic	28,469	25,581	28,389	25,106
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Incremental Common Shares Attributable to Stock Options	220	248	346	302
Incremental Common Shares Attributable to Deferred Compensation	217	237	202	207
Diluted Weighted Average Number of Shares Outstanding, Adjusted for Assumed Conversions	28,906	30,675	29,511	30,539
Earnings Per Share, Basic	$ 1.03	$ 0.74	$ 2.65	$ 2.00
Earnings Per Share, Diluted	$ 1.01	$ 0.64	$ 2.56	$ 1.73
Anti-dilutive stock equivalent awards not included in the calculation of diluted loss per share	437	0	363	31
2017 Convertible Senior Notes [Member]
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Interest on Convertible Debt, Net of Tax	$ 0	$ 324	$ 0	$ 1,106
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Incremental Common Shares Attributable to Conversion of Debt Securities	0	1,940	0	2,255
2018 Convertible Senior Notes [Member]
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Interest on Convertible Debt, Net of Tax	$ 0	$ 530	$ 408	$ 1,586
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Incremental Common Shares Attributable to Conversion of Debt Securities	0	2,669	574	2,669