Subsequent Events (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Apr. 05, 2017	Mar. 16, 2017	Mar. 31, 2017	Mar. 31, 2016
Subsequent Event [Line Items]
Dividend paid to common stockholders	$ 0.39		$ 0.36	$ 0.32
Dividends payable, date of record	Mar. 16, 2017	Mar. 16, 2017	Dec. 16, 2016	Dec. 17, 2015
Dividends payable, date payable	Apr. 05, 2017		Jan. 05, 2017	Jan. 06, 2016
Weighted average interest rate on floating rate debt			2.31%
Subsequent Event [Member] | Term Loan [Member]
Subsequent Event [Line Items]
Weighted average interest rate on floating rate debt	2.31%
Subsequent Event [Member] | Interest Rate Swap
Subsequent Event [Line Items]
Derivative instruments, notional amount	$ 400
Weighted average effective fixed interest rate	3.50%
Spread	1.50%
Subsequent Event [Member] | Interest Rate Swap | Term Loan [Member]
Subsequent Event [Line Items]
Aggregate principal amount	$ 400
Subsequent Event [Member] | Interest Rate Swap | Term Loan Maturing December 17,2021 [Member]
Subsequent Event [Line Items]
Derivative instruments, notional amount	200
Subsequent Event [Member] | Interest Rate Swap | Term Loan Maturing April 27, 2022 [Member]
Subsequent Event [Line Items]
Derivative instruments, notional amount	$ 200
Subsequent Event [Member] | Interest Rate Swap | LIBOR [Member]
Subsequent Event [Line Items]
Debt Instrument, Description of Variable Rate Basis	LIBOR