Earnings per Share Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share Calculation [Line Items]
Net Income, Including Portion Attributable to Noncontrolling Interest	$ 30,246	$ 17,723	$ 27,911	$ 18,063	$ 47,969	$ 45,974
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Net Income Available to Common Stockholders, Diluted	$ 30,246		$ 27,911		$ 47,969	$ 46,383
Weighted Average Number of Shares Outstanding, Basic	27,599		28,571		27,549	28,349
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Incremental Common Shares Attributable to Stock Options	308		353		276	409
Incremental Common Shares Attributable to Deferred Compensation	183		177		202	194
Diluted Weighted Average Number of Shares Outstanding, Adjusted for Assumed Conversions	28,090		29,101		28,027	29,818
Earnings Per Share, Basic	$ 1.10		$ 0.98		$ 1.74	$ 1.62
Earnings Per Share, Diluted	$ 1.08		$ 0.96		$ 1.71	$ 1.56
Anti-dilutive stock equivalent awards not included in the calculation of diluted loss per share	412		434		714	326
2018 Convertible Senior Notes [Member]
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Interest on Convertible Debt, Net of Tax	$ 0		$ 0		$ 0	$ 409
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Incremental Common Shares Attributable to Conversion of Debt Securities	0		0		0	866