Capital Stock - Schedule of Common Stock Activity (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Common Stock Activity [Roll Forward]
Beginning balance			$ 211,806
Ending balance	$ 218,801		218,801
Common Stock
Common Stock Activity [Roll Forward]
Beginning balance	213,099	$ 200,002	211,806	$ 194,953
Stock compensation expense	3,340	2,085	6,086	7,692
Stock consideration in acquisition	921	0	921	0
Ending balance	218,801	204,171	218,801	204,171
Treasury Cost
Common Stock Activity [Roll Forward]
Beginning balance	300,919	297,350	296,390	296,081
Stock compensation expense	0	0	0	0
Stock consideration in acquisition	0	0	0	0
Ending balance	303,744	296,870	303,744	296,870
Restricted and performance stock awards \| Common Stock
Common Stock Activity [Roll Forward]
Restricted and performance stock awards	232	399	2,643	1,501
Restricted and performance stock awards \| Treasury Cost
Common Stock Activity [Roll Forward]
Restricted and performance stock awards	232	399	2,643	1,501
Stock options exercised \| Common Stock
Common Stock Activity [Roll Forward]
Stock compensation expense	1,372	2,246	2,330	2,790
Stock options exercised \| Treasury Cost
Common Stock Activity [Roll Forward]
Stock compensation expense	395	1,200	902	1,502
Treasury shares purchased \| Common Stock
Common Stock Activity [Roll Forward]
Treasury shares purchased	0	0	0	0
Treasury shares purchased \| Treasury Cost
Common Stock Activity [Roll Forward]
Treasury shares purchased	(148)	(1,162)	(7,595)	(3,835)
Employee stock purchase program \| Common Stock
Common Stock Activity [Roll Forward]
Employee stock purchase program	301	237	301	237
Employee stock purchase program \| Treasury Cost
Common Stock Activity [Roll Forward]
Employee stock purchase program	43	43	43	43
Share repurchase program \| Common Stock
Common Stock Activity [Roll Forward]
Treasury shares purchased	0	0	0	0
Share repurchase program \| Treasury Cost
Common Stock Activity [Roll Forward]
Treasury shares purchased	$ (3,347)	$ 0	$ (3,347)	$ 0

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Value of all classes of common stock held by shareholders. May be all or portion of the number of common shares authorized. These shares exclude common shares repurchased by the entity and held as treasury shares.

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