Significant Accounting Policies Earnings per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Significant Accounting Policies [Abstract]
Net income	$ 15,842	$ 15,868	$ 19,138	$ 19,734	$ 14,292	$ 12,434	$ 18,227	$ 16,588	$ 70,582	$ 61,541	$ 69,932
Weighted Average Number of Shares Outstanding, Basic									85,209	85,892	89,656
Basic EPS	$ 0.18	$ 0.19	$ 0.23	$ 0.23	$ 0.17	$ 0.15	$ 0.21	$ 0.19	$ 0.83	$ 0.72	$ 0.78
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									232	309	17
Net Income (Loss) Available to Common Stockholders, Diluted									$ 70,582	$ 61,541	$ 69,932
Weighted Average Number of Shares Outstanding, Diluted									85,441	86,201	89,673
Diluted EPS	$ 0.18	$ 0.19	$ 0.23	$ 0.23	$ 0.17	$ 0.14	$ 0.21	$ 0.19	$ 0.83	$ 0.71	$ 0.78