Organization and Basis of Presentation - Summary of Financial Securities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Equity securities:
Carrying Value	$ 6,800	$ 6,700
Held to maturity
Equity and Debt Securities, Amortized Cost	213,199	211,960
Equity and Debt Securities, Gross Unrealized Gain (Loss)	2,235	(2,415)
Equity and Debt Securities, Marketable Securities	215,434	209,545
Investment funds - debt securities [Member]
Equity securities:
Amortized Cost/Cost	27,837	31,934
Gross Unrealized Gain (Loss)	379	(568)
Carrying Value	28,216	31,366
Common stock and stock funds [Member]
Equity securities:
Amortized Cost/Cost	38,780	39,731
Gross Unrealized Gain (Loss)	1,836	(1,671)
Carrying Value	40,616	38,060
Investment funds - U.S. treasuries [Member]
Available for sale
Amortized Cost/Cost	7,445	8,983
Gross Unrealized Gain (Loss)	(11)	(31)
Carrying Value	7,434	8,952
Investment-grade unsecured bonds [Member]
Available for sale
Amortized Cost/Cost	1,048	4,125
Gross Unrealized Gain (Loss)	31	(145)
Carrying Value	1,079	3,980
Mortgage backed securities [Member]
Held to maturity
Amortized Cost/Cost	138,089	127,187
Gross Unrealized Gain (Loss)	0	0
Carrying Value	$ 138,089	$ 127,187

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