Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	247,073
Stock-Based Compensation Activity
Income tax benefit	$ 0.5	$ 0.8
Treasury Stock, Shares, Acquired	255,000
Treasury Stock Acquired, Average Cost Per Share	$ 38.04
Enable Midstream Partners [Member]
Stock-Based Compensation Activity
Proceeds from Equity Method Investment, Distribution	$ 36.7	35.3
Performance Shares [Member]
Stock-Based Compensation Activity
Compensation expense	$ 1.9	2.7
Total Shareholder Return [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	201,552
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 38.03
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	67,193
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 43.69
Stock-Based Compensation Activity
Compensation expense	$ 0.1	0.3
Share-based Payment Arrangement [Member]
Stock-Based Compensation Activity
Compensation expense	2.0	3.0
Total Shareholder Return [Member] \| Performance Shares [Member]
Stock-Based Compensation Activity
Compensation expense	1.7	2.2
Performance Units Related to Earnings Per Share [Member] \| Performance Shares [Member]
Stock-Based Compensation Activity
Compensation expense	$ 0.2	$ 0.5

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

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