Defined Contribution and 401(k) Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Contribution and 401(k) (Textual) [Abstract]
Total contribution by employees		$ 2.1	$ 1.5	$ 1.0
Retirement Savings Plan under Section 401 (k) [Member]
Additional Defined Contribution And 401(k) (Textual) [Abstract]
Percentage of maximum limit for employees to contribute their cash compensation	100.00%
Percentage of employers matching contribution	100.00%
Percentage of employee contribution	3.00%
Percentage of employee compensation plus matching contribution	50.00%
Percentage of additional employee contribution	2.00%
Total plan expenses		$ 2.0	$ 1.4	$ 0.9