Stock Repurchase Plan (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended			3 Months Ended		6 Months Ended
	Jan. 31, 2014	Jul. 31, 2013	Dec. 31, 2012	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013
Stock Repurchase Plan
Additional authorized amount of outstanding common stock to be repurchased		$ 150	$ 50
Authorized amount to repurchase outstanding common stock				48.3	40.0
Aggregate shares repurchased				1,151,218	896,653	1,573,588
Repurchased shares settled	148,990
Remaining amount of authorized under 2013 Repurchase Plan				61.7
Acquisition of treasury stock						$ 50