Share-Based Compensation (Options) (Details) - Stock options $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares
Number of Shares
Options outstanding, beginning balance (in shares) | shares	1,186
Options exercised (in shares) | shares	(589)
Options outstanding, ending balance (in shares) | shares	597
Weighted-Average Exercise Price
Options outstanding, beginning balance (usd per share) | $ / shares	$ 20.67
Options exercised (usd per share) | $ / shares	21.23
Options outstanding, ending balance (usd per share) | $ / shares	$ 20.12
Weighted Average Remaining Contractual Term
Options outstanding, Weighted Average Remaining Contractual Term (in years)	4 years 1 month 13 days
Aggregate Intrinsic Value
Options outstanding, Aggregate Intrinsic Value | $	$ 14,979