Stock-Based Compensation - Schedule of Stock Option Activity and Weighted Average Exercise Prices (Details) - Employee Stock Option $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($) $ / shares shares
Options
Outstanding at January 1, 2018 (in shares) | shares	1,156,763
Granted (in shares) | shares	174,439
Forfeited or expired (in shares) | shares	(60,448)
Exercised (in shares) | shares	(162,594)
Unearned performance-based options (in shares) | shares	(17,160)
Outstanding at June 30, 2018 (in shares) | shares	1,091,000
Options exercisable at June 30, 2018 (in shares) | shares	918,462
Weighted- Average Exercise Price
Outstanding at January 1, 2018 (in dollars per share) | $ / shares	$ 45.93
Granted (in dollars per share) | $ / shares	61.30
Forfeited or expired (in dollars per share) | $ / shares	50.21
Exercised (in dollars per share) | $ / shares	43.41
Unearned performance-based options (in dollars per share) | $ / shares	59.97
Outstanding at June 30, 2018 (in dollars per share) | $ / shares	48.19
Options exercisable at June 30, 2018 (in dollars per share) | $ / shares	$ 42.24
Weighted-Average Remaining Contractual Term (Years)
Weighted-average remaining contractual term, outstanding at June 30, 2018	4 years 5 months
Weighted-average remaining contractual term, options exercisable at June 30, 2018	2 years 5 months
Aggregate Intrinsic Value as of June 30, 2018
Aggregate intrinsic value outstanding at June 30, 2018 | $	$ 9,585
Aggregate intrinsic value of options exercisable at June 30, 2018 | $	$ 4,689