Earnings Per Share (Details) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reconciliation of Weighted-Average Diluted Shares Outstanding
Weighted average common shares outstanding - basic	65,957,000	65,749,000
Pro Forma Weighted Average Shares Outstanding, Diluted	65,957,000	66,117,000
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	689,000	94,000
Convertible Senior Note
Convertible Note, Shares To Be Received Upon Conversion (in thousands)	2,300,000
Convertible Note, Conversion Price	$ 85.39
Restricted stock
Reconciliation of Weighted-Average Diluted Shares Outstanding
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0	211,000
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	491,000	76,000
Convertible Note [Member]
Reconciliation of Weighted-Average Diluted Shares Outstanding
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0	157,000
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0
Other equity-based awards
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	198,000	18,000