Fair Value Measurements - Narrative (Details) - Senior - USD ($)	Jun. 30, 2020	Dec. 31, 2019
$400 Million Senior Notes Due 2022
Fair Value Measurements [Line Items]
Debt instrument face amount	$ 400,000,000	$ 400,000,000
$400 Million Senior Notes Due 2022 | Level 2
Fair Value Measurements [Line Items]
Debt instrument face amount	400,000,000
Debt instrument fair value	423,300,000	432,000,000.0
$400 Million Senior Unsecured Notes Due 2029
Fair Value Measurements [Line Items]
Debt instrument face amount	400,000,000	400,000,000
$400 Million Senior Unsecured Notes Due 2029 | Level 2
Fair Value Measurements [Line Items]
Debt instrument face amount	400,000,000
Debt instrument fair value	$ 400,600,000	$ 403,400,000