Recent Accounting Pronouncements Recent Accounting Pronouncements (Details) - USD ($)	3 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Additional income due to changes in accounting for equity investments	$ 89,000	$ 1,300,000	$ 3,200,000
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				$ 3,806,000
Retained Earnings [Member] | Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				$ 1,917,000
AOCI Including Portion Attributable to Noncontrolling Interest [Member] | Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	995,000
Accumulated Other Comprehensive Income (loss) [Member] | Adjustments for New Accounting Pronouncement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	3,800,000
Retained Earnings [Member] | Adjustments for New Accounting Pronouncement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 3,800,000