Significant Accounting Policies Recent Accounting Adjustments (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Income Tax Expense (Benefit)			$ 131	$ (60)	$ 344
ASU 2016-16 | Forecasted
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect on retained earnings	$ 2,000
ASU 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Income Tax Expense (Benefit)		$ 4,500