Dividend Payment Restrictions (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Parent [Line Items]
Retained Earnings, Unappropriated	$ 783.0
Dividends, Earnings Before Interest, Tax, Deprecation and Amortization Ratio, Threshold For Dividend Payment	2.0
EBITDA Interest Expense Ratio	3.7
EBITDA to Interest Expense Denominator	1.0
Dividends, Earnings Before Interest, Tax, Deprecation and Amortization Ratio at Period End	1.0
Subsidiaries [Member]
Parent [Line Items]
Dividends, Common Equity Ratio, Threshold For Dividend Payment	44.00%
Dividends, Earnings Before Interest, Tax, Deprecation and Amortization Ratio, Threshold For Dividend Payment	3.0
Dividends, Common Equity Ratio at Period End	47.60%
EBITDA Interest Expense Ratio	5.6
EBITDA to Interest Expense Denominator	1.0
Dividends, Earnings Before Interest, Tax, Deprecation and Amortization Ratio at Period End	1.0