Fair Value Measurements - Narrative (Details) - Senior - USD ($)	Dec. 31, 2020	Jul. 23, 2020	Jul. 10, 2020	Jul. 09, 2020	Dec. 31, 2019	Nov. 27, 2019	Jun. 27, 2012
$400 million senior unsecured notes due 2022 with an effective interest rate of 6.0% less deferred issuance costs of $0.7 million and $2.3 million at December 31, 2020 and December 31, 2019, respectively
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, face amount	$ 400,000,000				$ 400,000,000		$ 400,000,000
Debt instrument, repurchased face amount		$ 183,400,000	$ 180,000,000.0	$ 160,000,000.0
Promissory note outstanding	216,600,000
$400 million senior unsecured notes due 2029 with an effective interest rate of 3.88%, less a discount and deferred issuance costs of $5.4 million and $6.0 million at December 31, 2020 and December 31, 2019, respectively
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, face amount	400,000,000				400,000,000	$ 400,000,000
$450 million senior unsecured notes due 2031 with an effective interest rate of 3.86%, less a discount and deferred issuance costs of $6.1 million at December 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, face amount	450,000,000	$ 450,000,000
Fair Value, Level 2 | $400 million senior unsecured notes due 2022 with an effective interest rate of 6.0% less deferred issuance costs of $0.7 million and $2.3 million at December 31, 2020 and December 31, 2019, respectively
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, face amount	400,000,000
Debt instrument, fair value	232,400,000				432,000,000.0
Fair Value, Level 2 | $400 million senior unsecured notes due 2029 with an effective interest rate of 3.88%, less a discount and deferred issuance costs of $5.4 million and $6.0 million at December 31, 2020 and December 31, 2019, respectively
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, face amount	400,000,000
Debt instrument, fair value	438,100,000				$ 403,400,000
Fair Value, Level 2 | $450 million senior unsecured notes due 2031 with an effective interest rate of 3.86%, less a discount and deferred issuance costs of $6.1 million at December 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, face amount	450,000,000
Debt instrument, fair value	$ 498,300,000