Capital Stock and Share-Based Compensation - Performance Stock Units Issued and Outstanding (Details) - 2010 Incentive Award Plan - Performance Stock Units $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Performance Stock Units
Unvested, Beginning Balance | shares	89	[1]
Granted | shares	48	[1]
Unvested, Ending Balance | shares	137	[1]
Expected to vest at end of period | shares	167	[1]
Weighted Average Grant Date Fair Value
Unvested, Beginning Balance | $ / shares	$ 24.00
Granted | $ / shares	62.17
Unvested, Ending Balance | $ / shares	37.28
Expected to vest at end of period | $ / shares	$ 33.21
Weighted Average Remaining Vesting Period (in years)
Unvested at end of period	1 year 1 month 20 days
Expected to vest at end of period	1 year 1 month 20 days
Aggregate Intrinsic Value
Unvested at end of period | $	$ 8,645	[2]
Expected to vest at end of period | $	$ 10,491	[2]

[1] The unvested PSUs are shown in this table at target, except for the number of shares vested, which reflect the shares earned and number of shares expected to vest. As of December 31, 2018, the maximum number of PSUs available to be earned is approximately 274 thousand.

[2] The aggregate intrinsic value is calculated based on the fair value of $63.00 per share of the Company’s common stock on December 31, 2018 due to the fact that the performance stock units carry a $0 purchase price