Equity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Shares Issued	23,416,396		23,416,396
Total Equity, beginning balance	$ 404,245	$ 394,232
Net income (loss) available for common stock	15,497	11,760
Other comprehensive income (loss), net of tax	12	27
Cumulative effect of ASU 2016-02, Leases implementation	(7)
Non-cash dividend to Parent company		(16,000)
Other adjustments	1	1
Total Equity, ending balance	$ 419,748	$ 390,020
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Shares Issued	23,416,000	23,416,000	23,416,000	23,416,000
Total Equity, beginning balance	$ 23,416	$ 23,416
Total Equity, ending balance	23,416	23,416
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total Equity, beginning balance	39,575	39,575
Total Equity, ending balance	39,575	39,575
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total Equity, beginning balance	342,145	332,499
Net income (loss) available for common stock	15,497	11,760
Cumulative effect of ASU 2016-02, Leases implementation	(7)
Non-cash dividend to Parent company		(16,000)
Other adjustments	1	1
Total Equity, ending balance	357,636	328,260
AOCI Attributable to Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total Equity, beginning balance	(891)	(1,258)
Other comprehensive income (loss), net of tax	12	27
Total Equity, ending balance	$ (879)	$ (1,231)