Earnings Per Share (Details) shares in Thousands			3 Months Ended		9 Months Ended
	Sep. 12, 2016 shares	Nov. 15, 2010 shares $ / shares	Sep. 30, 2016 shares	Sep. 30, 2015 shares	Sep. 30, 2016 shares	Sep. 30, 2015 shares	Mar. 15, 2021 $ / shares
Reconciliation of Weighted-Average Diluted Shares Outstanding
Weighted average common shares outstanding - basic			48,839	40,085	45,741	38,837
Weighted Average Number of Shares Outstanding - Diluted			48,839	40,085	45,741	38,837
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			757	1,379	1,153	1,438
Restricted stock
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			660	816	705	836
3.25% Convertible Note [Member]
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			0	468	345	505
Other equity-based awards
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			97	95
Stock Appreciation Rights [Member]
Anti-dilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount					103	97
1.125% Convertible Senior Notes due 2021 [Member]
Convertible Senior Note Due 2016
3.25% Convertible Note, Shares To Be Received Upon Conversion (in thousands)	2,300
3.25% Convertible Note, Conversion Price | $ / shares							$ 85.39
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
3.25% Convertible Note, Conversion Price | $ / shares		$ 42.40