Stock-Based Compensation Stock Option Summary (Details) - Employee Stock Option [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
[Line Items]
Outstanding, beginning balance, Number	959	1,180	1,123
Outstanding, beginning balance, Weighted Average Exercise Price Per Share	$ 45.64	$ 48.31	$ 51.90
Outstanding, beginning balance, Aggregate Intrinsic Value	$ 19,125	$ 405	$ 1,676
Granted, Number	135	191	291
Granted, Weighted Average Exercise Price Per Share	$ 65.94	$ 40.40	$ 35.25
Granted, Weighted Average Grant Date Fair Value	$ 21.99	$ 13.27	$ 12.09
Exercised, Number	(41)	(58)	(24)
Exercised, Weighted Average Exercise Price Per Share	$ 39.92	$ 37.00	$ 36.05
Exercised, Aggregate Intrinsic Value	$ 1,071	$ 742	$ 26
Forfeited, Number	(35)	(36)	(17)
Forfeited, Weighted Average Exercise Price Per Share	$ 47.38	$ 35.29	$ 37.47
Expired, Number	(62)	(318)	(193)
Expired, Weighted Average Exercise Price Per Share	$ 70.12	$ 55.13	$ 52.17
Outstanding, ending balance, Number	956	959	1,180	1,123
Outstanding, ending balance, Weighted Average Exercise Price Per Share	$ 47.10	$ 45.64	$ 48.31	$ 51.90
Outstanding, ending balance, Weighted Average Remaining Contractual Term	6 years 3 months 22 days	6 years 7 months	5 years 8 months 22 days	4 years 4 months 22 days
Outstanding, ending balance, Aggregate Intrinsic Value	$ 21,965	$ 19,125	$ 405	$ 1,676
Exercisable, Number	640
Exercisable, Weighted Average Exercise Price Per Share	$ 46.08
Exercisable, Weighted Average Remaining Contractual Term	5 years 3 months 22 days
Exercisable, Aggregate Intrinsic Value	$ 15,934
Expected to Vest [Member]
[Line Items]
Outstanding, ending balance, Number	316
Outstanding, ending balance, Weighted Average Exercise Price Per Share	$ 49.17
Outstanding, ending balance, Weighted Average Remaining Contractual Term	8 years 4 months 22 days
Outstanding, ending balance, Aggregate Intrinsic Value	$ 6,031