Employee Benefit Plans Fair Values of Pension Plan Assets, Classified in the Fair Value Hierarchy (Details) (Pension Plans, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total	$ 183,671		$ 168,408		$ 187,150
Fixed income securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fixed income securities	183,721	[1]	168,432	[2]
Accounts payable – pending trades	(50)		(24)
Total	183,671		168,408
Fixed income securities | Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fixed income securities	15,839	[1]	15,629	[2]
Fixed income securities | Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fixed income securities	167,882	[1]	152,803	[2]
Fixed income securities | Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fixed income securities	$ 0	[1]	$ 0	[2]

[1] Fixed income securities are comprised of corporate bonds (75%), government bonds (17%), government agencies securities (4%) and other fixed income securities (4%).

[2] Fixed income securities are comprised of corporate bonds (71%), government bonds (20%), government agencies securities (5%) and other fixed income securities (4%).