Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 09, 2011	Dec. 06, 2010
Estimate of Fair Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of our revolving facility and senior debt	$ 886.3
Reported Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of our revolving facility and senior debt	$ 861.0
3.2% Senior Notes, due June 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	3.20%
3.37% Senior Notes, due June 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	3.37%
4.5% Senior Notes, due December 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	4.50%		4.50%
4.2% Senior Notes, due December 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	4.20%	4.20%