Capital Stock And Share-Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended		0 Months Ended		12 Months Ended				12 Months Ended									3 Months Ended			12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Jun. 07, 2007 Minimum [Member]	Jun. 07, 2007 Maximum [Member]	Dec. 31, 2011 Maximum [Member]	Dec. 31, 2011 Share-Based Awards [Member] years months	Dec. 31, 2011 Share-Based Awards [Member] Minimum [Member]	Dec. 31, 2011 Share-Based Awards [Member] Maximum [Member]	Dec. 31, 2011 Employee Stock Purchase Plan [Member]	Dec. 31, 2010 Employee Stock Purchase Plan [Member]	Dec. 31, 2009 Employee Stock Purchase Plan [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2009 Stock Options [Member]	Dec. 31, 2011 Non-Vested Stock [Member] years	Dec. 31, 2010 Non-Vested Stock [Member]	Dec. 31, 2009 Non-Vested Stock [Member]	Jun. 30, 2011 Non-Vested Stock Units [Member]	Jun. 30, 2010 Non-Vested Stock Units [Member]	Jun. 30, 2009 Non-Vested Stock Units [Member]	Dec. 31, 2011 Non-Vested Stock Units [Member] years	Dec. 31, 2010 Non-Vested Stock Units [Member]	Dec. 31, 2009 Non-Vested Stock Units [Member]	Dec. 31, 2011 Share-Based Awards To More Than Ten Percent Owners [Member] Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized to issue	60,000,000	60,000,000
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares issued	31,017,363	29,867,701
Preferred stock, shares issued	0	0
Preferred stock, shares authorized to issue	5,000,000	5,000,000
Preferred stock, par value	$ 0.001	$ 0.001
Common stock, shares outstanding	30,328,549	29,232,807
Percentage of ownership in subsidiaries						50.00%
Preferred stock, shares outstanding	0	0
Equity-based awards, maximum number of shares granted								1,900,000
Equity-based awards, available for grant, shares						915,646
Fair value of a share of common stock, percentage							100.00%																	110.00%
Percentage of total combined voting power of us and our subsidiaries							10.00%
Equity-based award vesting period, minimum period						12									1						3
Equity-based award vesting period, maximum period, years						5									5						4
Contractual term of stock options exercised					ten years
Percentage of fair market value at which eligible employees may purchase shares of common stock									85.00%
Stock available for future issuance									357,777
Issuance of stock-employee stock purchase plan, shares			1,333,333	2,500,000					2,142,223
Employee stock purchase plan expenses									$ 0.8	$ 1.1	$ 1.0
Stock compensation plan expense															7.2	7.6	4.4				0.3	2.0	2.4
Total intrinsic value of options exercised												0.3
Stock options exercised, value												0.7	4.3	5.1
Unrecognized compensation cost related to non-vested stock award payments															$ 7.9						$ 0.2
Shares of stock are issued to the recipient until the stock unit awards have vested	0
Non-vested stock award payments, weighted-average period, years															1.6						0.3
Number of stock units authorized for achievement of targeted performance																		61,583	25,754	57,319
Performance based award share amount earned																					17,449	31,390
Number of stock units authorized for exceeding targeted performance																		92,376	38,631	85,977
Performance based objectives, percentage of target met																					81.50%	54.80%