Employee Benefit Plans Fair Values of Pension Plan Assets, Classified in the Fair Value Hierarchy (Details) - Pension Plans, Defined Benefit - USD ($) $ in Thousands		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total		$ 157,714		$ 154,506		$ 183,671
Fixed income securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fixed income securities		158,913	[1]	150,542	[2]
Defined Benefit Plan, Investments Measured at Net Asset Value		5,455		3,429
Accounts receivable – pending trades		(6,654)		535
Total		157,714		154,506
Fixed income securities | Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fixed income securities		16,427	[1]	16,028	[2]
Fixed income securities | Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fixed income securities		$ 142,486	[1]	134,514	[2]
Fixed income securities | Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fixed income securities	[1],[2]			$ 0

[1] Fixed income securities are comprised of corporate bonds (87%), government bonds (4%), government agency securities (2%) and other fixed income securities (7%).

[2] Fixed income securities are comprised of corporate bonds (96%), government agency securities (2%) and other fixed income securities (2%).