Earnings Per Share (Details)		3 Months Ended		9 Months Ended		12 Months Ended
	Nov. 15, 2010 shares $ / shares	Sep. 30, 2017 shares	Sep. 30, 2016 shares	Sep. 30, 2017 shares	Sep. 30, 2016 shares	Dec. 31, 2016 shares $ / shares
Reconciliation of Weighted-Average Diluted Shares Outstanding
Weighted average common shares outstanding - basic		65,865,000	48,839,000	65,825,000	45,741,000
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		636,000	757,000	667,000	1,153,000
Convertible Senior Note Due 2016
3.25% Convertible Note, Shares To Be Received Upon Conversion (in thousands)						2,300,000
3.25% Convertible Note, Conversion Price | $ / shares						$ 85.39
Restricted stock
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		588,000	660,000	585,000	705,000
3.25% Convertible Note [Member]
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		0	0	0	345,000
Other equity-based awards
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		48,000	97,000	82,000	103,000
3.25% Convertible Senior Notes due 2016 [Member]
Convertible Senior Note Due 2016
3.25% Convertible Note, Shares To Be Received Upon Conversion (in thousands)	2,700,000
3.25% Convertible Note, Conversion Price | $ / shares	$ 42.40