Assets and Liabilities Measured at Fair Value (Nonrecurring Fair Value Measurements) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets and Liabilities Measured at Fair Value [Abstract]
Total Pretax (Noncash) Impairment Expense	$ 20,000,000	$ 0	$ 95,088,000	[1]

[1] Reclassified to conform to current presentation (see Note B).