Options and Awards Restricted Awards Granted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted awards granted [Line Items]
Restricted Awards Grant Date Fair Value Range, Minimum	$ 18.47	$ 18.79	$ 21.00
Restricted Awards Grant Date Fair Value Range, Maximum	$ 22.90	$ 23.23	$ 26.55
Share-based Compensation, Restricted Awards, Exercise Price	$ 0
Issuance of restricted stock to employees (in shares)	173	299	323
Award Vesting Period	5 years
Director [Member]
Restricted awards granted [Line Items]
Restricted Awards Grant Date Fair Value Range, Minimum	$ 18.47
Restricted Awards Grant Date Fair Value Range, Maximum	$ 21.96
Options Granted to Non-employee Directors	30