Fair Value Measurement (Narrative) (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) agreement	Dec. 31, 2019 USD ($)
Credit Derivatives [Line Items]
Fair value of funded deferred compensation assets	$ 22,600,000	$ 26,900,000
Separate line of credit agreements (in agreements) | agreement	1
Fair Value, Measurements, Nonrecurring
Credit Derivatives [Line Items]
Fair value, net asset (liability)	$ 0	$ 0
Corporate debt, limited observable inputs | NRSRO, Rating BBplus
Credit Derivatives [Line Items]
Credit rating	100.00%
Corporate debt, limited observable inputs | NRSRO, Rating BBBminus
Credit Derivatives [Line Items]
Credit rating		66.00%
Other asset-backed securities | NRSRO, Rating AAminus
Credit Derivatives [Line Items]
Credit rating	75.00%
Other asset-backed securities | NRSRO, Rating AA
Credit Derivatives [Line Items]
Credit rating		100.00%
Interest Rate Cap
Credit Derivatives [Line Items]
Premium paid on derivative for right to receive cash payments	$ 2,000,000
Floor interest rate on derivative	2.35%
Interest Rate Cap | Other assets
Credit Derivatives [Line Items]
Derivative asset, notional amount	$ 35,000,000