Capital Stock - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended		230 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Dec. 31, 2016
Equity [Abstract]
Shares repurchased	3,000,000		32,900,000
Treasury stock repurchases (in usd)	$ 68,255	$ 0	$ 456,600
Shares authorized for repurchase	40,000,000		40,000,000
Shares retired			20,000,000
Treasury stock	12,935,926		12,935,926	9,892,680