Stockholders' Equity (Changes in Common Stock Shares Outstanding) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Class of Stock [Line Items]
Total stockholders’ equity	$ 1,556,320us-gaap_StockholdersEquity	$ 1,447,948us-gaap_StockholdersEquity	$ 1,391,680us-gaap_StockholdersEquity
Common Stock [Member]
Class of Stock [Line Items]
Total stockholders’ equity	3,635	3,635	3,635
Shares exercised under stock option plan	1	0	0
Total stockholders’ equity	$ 3,636	$ 3,635	$ 3,635

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References+ Details

Value of stock (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of stock value of such awards forfeited. Stock issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

+ References+ Details