Income Taxes (Narrative) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Income tax expense	$ 9,574,000	$ 945,000
Effective tax rate		7.40%
Tax benefit from exercise of stock option awards	$ (300,000)	$ 300,000
Change in effective tax rate		16.40%
Provisional tax expense (benefit) for impact of the Tax Act of 2017		$ 2,100,000
Statutory corporate tax rate	21.00%		35.00%
Income tax interest and penalties	$ 26,000	$ 0
Deferred tax assets, valuation allowance	9,800,000
Without Valuation Allowance [Member]
Income Tax Contingency [Line Items]
Income tax expense	$ 200,000