Earnings Per Share Reconciliation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
NUMERATOR
Net income (loss) from continuing operations	$ 23,527	$ 22,004
Net income from discontinued operations	0	113
Less: distributed earnings allocated to nonvested restricted stock	0	(3)
Less: undistributed earnings allocated to nonvested restricted stock	(30)	(111)
Numerator for basic income per share	23,497	22,003
Plus: undistributed earnings allocated to nonvested restricted stock	30	111
Less: undistributed earnings reallocated to nonvested restricted stock	(24)	(95)
Numerator for diluted income per share	24,531	22,748
DENOMINATOR
Basic earnings per share-weighted-average shares	46,579,280	45,434,996
Effect of dilutive securities:
Share-based payments (in shares)	957,906	903,321
Diluted earnings per share-adjusted weighted-average shares and assumed conversions	58,126,928	53,362,097
NET INCOME PER COMMON SHARE
Basic (in dollars per share)	$ 0.50	$ 0.48
Diluted (in dollars per share)	$ 0.42	$ 0.43
1.6 percent convertible senior notes due 2018
NUMERATOR
Plus: interest on convertible senior notes	729	729
Effect of dilutive securities:
Convertible senior notes (in shares)	7,023,780	7,023,780
NET INCOME PER COMMON SHARE
Interest rate stated percentage	1.60%
0.25 percent convertible senior notes due 2019
NUMERATOR
Plus: interest on convertible senior notes	$ 299	$ 0
Effect of dilutive securities:
Convertible senior notes (in shares)	3,565,962	0
NET INCOME PER COMMON SHARE
Interest rate stated percentage	0.25%