Long Term Debt - Senior Unsecured Notes (Details) - Senior Unsecured Notes [Member]	Jul. 17, 2014 USD ($)
The 2024 Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount	$ 300,000,000
Debt instrument, interest rate, stated percentage	3.749%
The 2034 Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount	$ 300,000,000
Debt instrument, interest rate, stated percentage	4.915%
The 2044 Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount	$ 900,000,000
Debt instrument, interest rate, stated percentage	5.165%