Reinsurance and Policy Benefits and Losses Claims and Loss Expenses Payable (Policy Benefits and Losses, Claims and Loss Expenses Payable for Property and Casualty Insurance) (Details) - USD ($) $ in Thousands	Mar. 31, 2017		Dec. 31, 2016	Mar. 31, 2016		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reinsurance:
Unpaid losses and loss adjustment expense			$ 244,400			$ 251,964
Total	$ 1,086,322			$ 1,071,412
Operating Segments [Member] | Property and Casualty Insurance [Member]
Reinsurance:
Unpaid losses and loss adjustment expense			244,400			251,964	$ 271,609	$ 295,126
Reinsurance losses payable			580			855
Total	$ 244,980	[1]	$ 244,980	$ 252,819	[2]	$ 252,819

[1] Balances as of December 31, 2016

[2] Balances as of December 31, 2015