Stock-based Compensation Expense Fixed-Price Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Shares
Outstanding Shares,Beginning Balance (in shares)	1,676,927
Granted (in shares)	141,661	313,803	222,939
Exercised (in shares)	(212,343)
Forfeited (in shares)	(64,001)
Outstanding Shares, Ending Balance (in shares)	1,542,244	1,676,927
Exercisable, Ending Balance (in shares)	858,291
Weighted-Average Exercise Price
Outstanding Weighted-Average Exercise Price, Beginning Balance (in dollars per share)	$ 50.76
Granted (in dollars per share)	56.56
Exercised (in dollars per share)	44.28
Forfeited (in dollars per share)	59.03
Outstanding Weighted-Average Exercise (in dollars per share)Price, Ending Balance	51.85	$ 50.76
Exercisable Weighted-Average Exercise Price, Ending Balance (in dollars per share)	$ 45.63
Weighted-Average Remaining Contractual Term (Years)
Weighted-Averaged Remaining Contractual Term, Beginning Balance	5 years 6 months	6 years 1 month 6 days
Weighted-Averaged Remaining Contractual Term, Ending Balance	5 years 6 months	6 years 1 month 6 days
Exercisable Weighted-Average Remaining Contractual Term, Ending Balance	3 years 8 months 24 days
Aggregate Intrinsic Value
Outstanding Aggregate Intrinsic Value, Beginning Balance	$ 14,152
Outstanding Aggregate Intrinsic Value, Ending Balance	52,798	$ 14,152
Exercisable Aggregate Intrinsic Value, Ending Balance	$ 34,720