Stock-Based Compensation Plans - Activity of Stock Options Exercisable and Outstanding (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest [Abstract]
Exercisable and vested options at period end, shares under option (in shares) | shares	9
Exercisable and vested options at period end, remaining contractual life (in years)	2 years 3 months 18 days
Exercisable and vested options at period end, average exercise price per share (in dollars per share)	$ 48.37
Exercisable and vested options at period end, intrinsic value per share (in dollars per share)	$ 93.12	[1]
Exercisable and vested options at period end, aggregate intrinsic value | $	$ 800
Common stock, market fair value (in dollars per share)	$ 141.49

[1] Computed based upon the amount by which the fair market value of our common stock on December 31, 2015 of $141.49 per share exceeded the weighted average exercise price.