Stock-Based Compensation - Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of Options (in 000's)
Outstanding at beginning of the year (in shares)		648	650	924
Granted (in shares)		243	77	133
Exercised (in shares)		(239)	(71)	(391)
Forfeited/canceled/expired (in shares)		0	(8)	(16)
Outstanding at end of the year (in shares)		652	648	650
Vested and expected to vest at the end of the year (in shares)		652	648	649
Exercisable at the end of the year (in shares)		363	493	421
Weighted-Average Exercise Price
Outstanding at beginning of the year (in dollars per share)		$ 30.50	$ 25.56	$ 22.04
Granted (in dollars per share)		49.67	64.81	35.28
Exercised (in dollars per share)		26.09	23.97	20.76
Forfeited/canceled/expired (in dollars per share)		0.00	20.64	20.77
Outstanding at end of the year (in dollars per share)		39.27	30.50	25.56
Vested and expected to vest at the end of the year (in dollars per share)		39.27	30.50	25.57
Exercisable at the end of the year (in dollars per share)		$ 30.21	$ 25.03	$ 23.84
Weighted-Average Remaining Contractual Term and Aggregate Intrinsic Value
Outstanding at end of the year, term		4 years 9 months 10 days	4 years 10 months 5 days	5 years 7 months 2 days
Vested and expected to vest at the end of the year, term		4 years 9 months 10 days	4 years 10 months 5 days	5 years 6 months 28 days
Exercisable at the end of the year, term		3 years 10 months 17 days	4 years 6 months 3 days	4 years 10 months 13 days
Exercised		$ 9,933	$ 2,193	$ 10,651
Outstanding at end of the year	[1]	16,553	14,556	25,653
Vested and expected to vest at the end of the year	[1]	16,548	14,551	25,618
Exercisable at the end of the year	[1]	$ 12,511	$ 12,979	$ 17,345

[1] The aggregate intrinsic value represents the total pre-tax value (the difference between our closing stock price on the last trading day of 2016, 2015, and 2014 and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had they all exercised their options on December 31, 2016, 2015, and 2014. This amount will change based on the fair market value of our stock.