Stock-Based Compensation - Option Activity (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Number of Options
Outstanding at beginning of the year	924		1,412		1,502
Granted	133		201		153
Exercised	(391)		(679)		(189)
Forfeited/canceled/expired	(16)		(10)		(54)
Outstanding at end of the year	650		924		1,412
Vested and expected to vest at the end of the year	649		921		1,409
Exercisable at the end of the year	421		671		1,181
Weighted-Average Exercise Price
Outstanding at beginning of the year	$ 22.04		$ 20.56		$ 19.53
Granted	$ 35.28		$ 19.68		$ 19.92
Exercised	$ 20.76		$ 18.22		$ 11.62
Forfeited/canceled/expired	$ 20.77		$ 24.75		$ 21.48
Outstanding at end of the year	$ 25.56		$ 22.04		$ 20.56
Vested and expected to vest at the end of the year	$ 25.57		$ 22.05		$ 20.56
Exercisable at the end of the year	$ 23.84		$ 22.62		$ 20.24
Weighted-Average Remaining Contractual Term and Aggregate Intrinsic Value
Outstanding at beginning of the year	5 years 7 months 2 days		6 years 1 month 3 days		4 years 10 months 28 days
Vested and expected to vest at the end of the year	5 years 6 months 28 days		6 years 0 months 28 days		4 years 10 months 24 days
Exercisable at the end of the year	4 years 10 months 13 days		5 years 1 month 20 days		4 years 3 months
Exercised	$ 10,651		$ 8,355		$ 1,155
Outstanding at end of the year	25,653	[1]	14,854	[1]	2,452	[1]
Vested and expected to vest at the end of the year	25,618	[1]	14,791	[1]	2,446	[1]
Exercisable at the end of the year	$ 17,345	[1]	$ 10,388	[1]	$ 2,347	[1]

[1] The aggregate intrinsic value represents the total pre-tax value (the difference between our closing stock price on the last trading day of 2014, 2013, and 2012 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, 2014, 2013, and 2012. This amount will change based on the fair market value of our stock.