Stockholders' Equity (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended
	Mar. 31, 2012 Employee Stock [Member]	Feb. 29, 2012 FourZeroOneKPlanMember [Member]	Mar. 31, 2012 Additional Paid-in Capital [Member]	Mar. 31, 2012 Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued in underwritten public offering (shares)	0.8	0.2		13.5
Net proceeds from issuance of common stock			$ 206.9
Share price of common stock contributed to ESOP (US$ per share)	$ 16.02	$ 15.53