Indebtedness (Details) (USD $)	0 Months Ended									0 Months Ended
	Apr. 14, 2014 Senior Notes Senior Unsecured Notes, 4.75% Note Due 2021	Apr. 14, 2014 Senior Notes Senior Unsecured Notes, 3.95% Due 2018	Apr. 14, 2014 Senior Notes Senior Unsecured Notes, 3.75% Note Due 2018	Jun. 30, 2014 Term Loan Line of Credit Credit Facility, 2014	Apr. 14, 2014 Term Loan Line of Credit Credit Facility, 2014	Jun. 30, 2014 Revolving Credit Facility Line of Credit Credit Facility, 2014	Apr. 14, 2014 Revolving Credit Facility Line of Credit Credit Facility, 2014	Apr. 12, 2014 Revolving Credit Facility Line of Credit Credit Facility, 2014	Dec. 31, 2013 Revolving Credit Facility Line of Credit Credit Facility, 2014	Apr. 14, 2014 Revolving Credit Facility Line of Credit Credit Facility, 2014 Minimum	Apr. 14, 2014 Revolving Credit Facility Line of Credit Credit Facility, 2014 Maximum	Apr. 14, 2014 Revolving Credit Facility Line of Credit Credit Facility, 2014 Libor Minimum	Apr. 14, 2014 Revolving Credit Facility Line of Credit Credit Facility, 2014 Libor Maximum	Apr. 14, 2014 Subfacility Line of Credit Credit Facility, 2014	Apr. 12, 2014 Subfacility Line of Credit Credit Facility, 2014	Apr. 14, 2014 Swingline Loan Subfacility Line of Credit Credit Facility, 2014	Apr. 12, 2014 Swingline Loan Subfacility Line of Credit Credit Facility, 2014
Debt Instrument [Line Items]
Line of credit facility, amount outstanding				$ 126,300,000	$ 126,300,000	$ 70,000,000			$ 0
Line of credit facility, current borrowing capacity							200,000,000	140,000,000						20,000,000	10,000,000	25,000,000	15,000,000
Line of credit facility, additional borrowing capacity							200,000,000
Debt instrument, basis spread on variable rate												1.75%	2.25%
Line of credit facility, unused capacity, commitment fee percentage										0.15%	0.30%
Debt instrument, face amount	300,000,000	125,000,000
Debt instrument, interest rate, stated percentage	4.75%	3.95%	3.75%
Debt instrument, periodic payment, principal	$ 60,000,000	$ 25,000,000