Stock Option Summary (Details) - Employee Stock Option [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended					9 Months Ended
		Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015		Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015
[Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term		5 years 5 months 15 days		1 day	[1]		5 years 5 months 15 days	5 years 5 months 15 days
Outstanding, beginning balance, Number				1,123			1,180	1,123
Outstanding, beginning balance, Weighted Average Exercise Price Per Share				$ 49.12			$ 48.31	$ 51.90
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term			5 years 8 months 2 days			4 years 4 months 22 days	6 years 10 months 2 days	5 years 5 months
Outstanding, beginning balance, Aggregate Intrinsic Value	[2]			$ 0			$ 405	$ 1,676
Options granted, number				0			191	207
Granted, Weighted Average Exercise Price Per Share							$ 40.40	$ 35.30
Granted, Weighted Average Grant Date Fair Value							$ 13.27	$ 12.15
Exercised, Number							(35)	(23)
Exercised, Weighted Average Exercise Price Per Share							$ 35.31	$ 36.05
Exercised, Aggregate Intrinsic Value	[2]						$ 214	$ 26
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares							(36)	(17)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Weighted Average Grant Date Fair Value							$ 35.29	$ 37.47
Expired, Number							(312)	(167)
Expired, Weighted Average Exercise Price Per Share							$ 55.11	$ 53.95
Outstanding, ending balance, Number		988	1,180			1,123	988
Outstanding, ending balance, Weighted Average Exercise Price Per Share		$ 45.57	$ 48.31			$ 51.90	$ 45.57
Outstanding, ending balance, Aggregate Intrinsic Value	[2]	$ 13,732	$ 405			$ 1,676	$ 13,732
Exercisable, Number		563					563
Exercisable, Weighted Average Exercise Price Per Share		$ 51.57					$ 51.57
Exercisable, Weighted Average Remaining Contractual Term							5 years 1 month 1 day
Exercisable, Aggregate Intrinsic Value	[2]	$ 6,024					$ 6,024
Expected to Vest [Member]
[Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term							8 years 11 months 2 days
Outstanding, ending balance, Number		410					410
Outstanding, ending balance, Weighted Average Exercise Price Per Share		$ 37.58					$ 37.58
Outstanding, ending balance, Aggregate Intrinsic Value	[2]	$ 7,448					$ 7,448

[1] There were no employee stock options granted for the three months ended September 30, 2015.

[2] The aggregate intrinsic value of outstanding stock options represents amounts that would have been received by the optionees had all in- the-money options been exercised on that date. Specifically, it is the amount by which the market value of our stock exceeded the exercise price of the outstanding in-the-money options before applicable income taxes, based on our closing stock price on the last business day of the period. The aggregate intrinsic value of stock options exercised during the period is calculated based on our stock price at the date of exercise.