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Stock-Based Compensation (Stock Options) (Details) - Stock options - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2016	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	3 years
Exercised (in shares)		0	0
Recognized stock-based compensation expense		$ 0	$ 0
Unrecognized stock-based compensation expense				$ 0
Proceeds from stock options exercised		$ 0	$ 0
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period (in years)	7 years