Shareholders' Equity and Stock Compensation (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Shareholders Equity and Share-Based Payments [Line Items]
Share-based Compensation, Excluding Accelerated Compensation Cost	$ 1,600	$ 2,500
Total income tax benefit recognized related to stock-based compensation	401	977
Proceeds from stock options exercised	759	230
Income tax benefits received	2,600	1,800
Employee Stock Option
Shareholders Equity and Share-Based Payments [Line Items]
Total intrinsic value of options exercised	658	112
Cash from stock options exercised	116	49
Proceeds from stock options exercised	759	230
Total unrecognized compensation cost related to nonvested stock awards	0
Restricted Stock
Shareholders Equity and Share-Based Payments [Line Items]
Total fair value of restricted stock shares/units vested and released	9,700	4,500
Total unrecognized compensation cost related to nonvested stock awards	$ 14,000
Expected recognized over a weighted-average period, years	2 years
Restricted Stock Units (RSUs)
Shareholders Equity and Share-Based Payments [Line Items]
Total fair value of restricted stock shares/units vested and released		$ 41
Total unrecognized compensation cost related to nonvested stock awards	$ 4
Expected recognized over a weighted-average period, years	4 days