Share-Based Compensation (Narrative) (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended									12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2012 SERP [Member]	Dec. 31, 2010 SERP [Member]	Dec. 31, 2009 Deferred Compensation Plan, Amendment Plan Year 2010 [Member]	Dec. 31, 2012 Deferred Compensation, Share-Based Payments [Member] SERP [Member]	Dec. 31, 2011 Deferred Compensation, Share-Based Payments [Member] SERP [Member]	Dec. 31, 2010 Deferred Compensation, Share-Based Payments [Member] SERP [Member]	Dec. 31, 2012 Stock Option [Member]	Dec. 31, 2011 Stock Option [Member]	Dec. 31, 2010 Stock Option [Member]	Dec. 31, 2012 Equity Incentive Stock Option Plans [Member]	Dec. 31, 2011 Equity Incentive Stock Option Plans [Member]	Dec. 31, 2010 Equity Incentive Stock Option Plans [Member]	Dec. 31, 2012 ESPP [Member]	Dec. 31, 2011 ESPP [Member]	Dec. 31, 2010 ESPP [Member]	Apr. 12, 2011 ESPP [Member] offering	Feb. 12, 2004 ESPP [Member] offering	Jan. 01, 2000 ESPP [Member] offering
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 2,538,000	[1]	$ 2,152,000	[1]	$ 1,332,000	[1]				$ 560,000	$ 444,000	$ 400,000	$ 1,897,000	$ 1,870,000	$ 1,015,000				$ 641,000	$ 282,000	$ 317,000
Percentage of match participants' deferrals							25.00%	25.00%
Common stock reserved for future issuance																5,969
Maximum term of grants																10 years
Options vested and exercisable, period, in years																5 years	5 years	5 years
Weighted average grant-date fair value of stock options granted																$ 4.74	$ 3.26	$ 3.98
Unrecognized compensation related to stock options	3,999,000		3,547,000		3,356,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Initial Offerings																								5
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Offerings																						5	8
Period of expense of unrecognized compensation cost, years	4 years		4 years		4 years
Stock options authorized to issue to employees																			4,050
Shares available for future grant																3,337			2,541
Annual earnings withheld to purchase Common Stock																			21,250
Percent of IRS limitation																			85.00%
Maximum fair value of common stock purchased																			$ 25,000
Percentage of stock purchase price																			85.00%
Percentage of earned income on a pre-tax basis, deferred					25.00%				15.00%
Percentage of deferral in the form of Common Stock					15.00%
Stock options authorized to issue							1,013
Common stock reserved for future issuance							471
Shares exercised and delivered	24
Shares forfeited for current year funding	9
Shares issued to trustee	541
Stock options vested and outstanding							282

[1] Stock-based compensation expense is recorded in the selling, general and administrative caption in our consolidated statements of comprehensive income.