New Accounting Standards Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 01, 2017	Jan. 01, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in accumulated other comprehensive income	$ 7,116	$ 13,914
Increase in income tax expense	53,918	34,895	$ 41,088
Decrease in other comprehensive income	(6,798)	5,913	$ 10,613
Increase in operating loss carryforward deferred tax assets	60,749	$ 35,153
Potential Impact of Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in retained earnings					$ 28,800
Decrease in accumulated other comprehensive income					$ 28,800
Increase in investment income	1,200
Increase in income tax expense	200
Decrease in other comprehensive income	$ 1,000
Subsequent Event | Potential Impact of Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in retained earnings				$ 200
Increase in operating loss carryforward deferred tax assets				$ 200