Stock-Based Compensation - Schedule of Summary of Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Shares (in thousands)
Outstanding at January 1, 2016 (in shares) | shares	874
Exercised (in shares) | shares	(522)
Forfeited (in shares) | shares	(13)
Outstanding at December 31, 2016 (in shares) | shares	339
Exercisable at December 31, 2016 (in shares) | shares	338
Vested or expected to vest December 31, 2016 (in shares) | shares	339
Weighted Average Exercise Price
Outstanding at January 1, 2016 (in dollars per share) | $ / shares	$ 35.51
Exercised (in dollars per share) | $ / shares	34.68
Forfeited (in dollars per share) | $ / shares	47.26
Outstanding at December 31, 2016 (in dollars per share) | $ / shares	36.36
Exercisable at December 31, 2016 (in dollars per share) | $ / shares	36.31
Vested or expected to vest December 31, 2016 (in dollars per share) | $ / shares	$ 36.35
Weighted Average Remaining Contractual Term & Aggregate Intrinsic Value
Outstanding at December 31, 2017	1 year 7 months 28 days
Exercisable at December 31, 2017	1 year 7 months 28 days
Vested or expected to vest December 31, 2017	1 year 7 months 28 days
Outstanding at December 31, 2017 | $	$ 9,734
Exercisable at December 31, 2017 | $	9,708
Vested or expected to vest December 31, 2017 | $	$ 9,731