Summary of Significant Accounting Policies, Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018
Recently Adopted Accounting Pronouncements [Abstract]
Restricted cash	$ 6,815	$ 6,815	$ 4,033
Corporate income tax rate		21.00%	35.00%
Goodwill, Impairment Loss	3,152	$ 3,152	$ 0	$ 0
ASU 2016-01 [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Cumulative-effect adjustment to reclassify unrealized gains on equity securities after tax			0
ASU 2016-18 [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Restricted cash			4,000
ASU 2018-02 [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Cumulative-effect adjustment to reclassify unrealized gains on equity securities after tax			0		$ (117)
ASU 2017-04 [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Goodwill, Impairment Loss	3,152
ASU 2016-02 [Member] | Plan [Member]
Recently Issued Accounting Pronouncements [Abstract]
Right-of-use asset	400	400
Lease liability	$ 400	$ 400
Other Comprehensive Income (Loss) [Member] | ASU 2016-01 [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Cumulative-effect adjustment to reclassify unrealized gains on equity securities before tax			(71,012)
Cumulative-effect adjustment to reclassify unrealized gains on equity securities after tax			(46,157)
Other Comprehensive Income (Loss) [Member] | ASU 2018-02 [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Cumulative-effect adjustment to reclassify unrealized gains on equity securities after tax			117		$ 117
Retained Earnings [Member] | ASU 2016-01 [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Cumulative-effect adjustment to reclassify unrealized gains on equity securities before tax			71,012
Cumulative-effect adjustment to reclassify unrealized gains on equity securities after tax			46,157
Retained Earnings [Member] | ASU 2018-02 [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Cumulative-effect adjustment to reclassify unrealized gains on equity securities after tax			$ (117)