Summary of Significant Accounting Policies (Earnings Per Share) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 16, 2014	Mar. 08, 2012	May. 31, 2011	May. 02, 2011
Accounting Policies [Abstract]
Common stock equivalents (in shares)	1,146,000	1,175,000	949,000
Anti-dilutive securities excluded from computation of diluted earnings per share (in shares)	18,000	715,000	941,000
Stock repurchase program authorized amount	$ 400,000,000.0			$ 257,800,000	$ 323,700,000.0	$ 300,000,000	$ 300,000,000
Stock repurchase program remaining authorized repurchase amount	$ 306,200,000	$ 400,000,000		$ 400,000,000.0