Significant Accounting Policies Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Significant Accounting Policies [Abstract]
Net income	$ 22,440	$ 19,056	$ 17,803	$ 13,378	$ 38,605	$ 7,916	$ 14,616	$ 14,036	$ 72,677	$ 75,173	$ 56,386
Weighted Average Number of Shares Outstanding, Basic									82,378	83,298	83,297
Basic EPS	$ 0.27	$ 0.23	$ 0.22	$ 0.16	$ 0.45	$ 0.10	$ 0.18	$ 0.17	$ 0.88	$ 0.90	$ 0.68
Dilutive Securities, Effect on Basic Earnings Per Share, Including Options and Restrictive Stock Units									$ 0	$ 0	$ 0
Incremental Common Shares Attributable to Share-based Payment Arrangements									32	38	68
Net Income (Loss) Available to Common Stockholders, Diluted									$ 72,677	$ 75,173	$ 56,386
Weighted Average Number of Shares Outstanding, Diluted									82,410	83,336	83,365
Diluted EPS	$ 0.27	$ 0.23	$ 0.22	$ 0.16	$ 0.45	$ 0.09	$ 0.18	$ 0.17	$ 0.88	$ 0.90	$ 0.68