Income Taxes (Earliest Tax Year) (Detail)	12 Months Ended
	Dec. 31, 2020
Pennsylvania
Operation In Major Geographical Areas Tax Year [Line Items]
Earliest Open Tax Year	2012
Connecticut
Operation In Major Geographical Areas Tax Year [Line Items]
Earliest Open Tax Year	2017
Virginia
Operation In Major Geographical Areas Tax Year [Line Items]
Earliest Open Tax Year	2017
West Virginia
Operation In Major Geographical Areas Tax Year [Line Items]
Earliest Open Tax Year	2017
New York
Operation In Major Geographical Areas Tax Year [Line Items]
Earliest Open Tax Year	2015
Utah
Operation In Major Geographical Areas Tax Year [Line Items]
Earliest Open Tax Year	2017
South Carolina
Operation In Major Geographical Areas Tax Year [Line Items]
Earliest Open Tax Year	2013