Fair Value Measurements (Details 1) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and Cash Equivalents, Fair Value Disclosure	$ 45,093	$ 200,526
Available-for-sale Securities, Fair Value Disclosure	227,805	312,888
Investments, Fair Value Disclosure	272,898	513,414
Accrued Liabilities, Fair Value Disclosure	0	0
Other Liabilities, Fair Value Disclosure		0
Liabilities, Fair Value Disclosure	0	0
Fair Value, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and Cash Equivalents, Fair Value Disclosure	1,507	2,463
Available-for-sale Securities, Fair Value Disclosure	72,099	5,475
Investments, Fair Value Disclosure	73,606	7,938
Accrued Liabilities, Fair Value Disclosure	0	0
Other Liabilities, Fair Value Disclosure		0
Liabilities, Fair Value Disclosure	0	0
Fair Value, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Available-for-sale Securities, Fair Value Disclosure	0	0
Investments, Fair Value Disclosure	0	0
Accrued Liabilities, Fair Value Disclosure	18,912	12,453
Other Liabilities, Fair Value Disclosure		10,362
Liabilities, Fair Value Disclosure	18,912	22,815
Fair Value, Total
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and Cash Equivalents, Fair Value Disclosure	46,600	202,989
Available-for-sale Securities, Fair Value Disclosure	299,904	318,363
Investments, Fair Value Disclosure	346,504	521,352
Accrued Liabilities, Fair Value Disclosure	18,912	12,453
Other Liabilities, Fair Value Disclosure		10,362
Liabilities, Fair Value Disclosure	$ 18,912	$ 22,815