Retirement and Other Benefit Plans (Details) $ in Millions |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2018
USD ($)
plan
|
Dec. 31, 2017
USD ($)
Agreement
|
Dec. 31, 2016
USD ($)
Agreement
|
|
Retirement Benefits [Abstract] | |||
Number of defined contribution plans maintained by the company | 4 | 4 | 4 |
Defined contribution retirement plan cost | $ 31.2 | $ 27.6 | $ 23.7 |