Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share
Net income for basic and diluted earnings per share	$ 13,620	$ 8,622
Shares of common stock and common stock equivalents:
Average common shares used in basic computation	36,081,000	37,378,000
Effect of dilutive securities (in shares)	1,104,000	1,237,000
Average common shares used in diluted computation	37,185,000	38,615,000
Earnings per share:
Basic (in dollars per share)	$ 0.38	$ 0.23
Diluted (in dollars per share)	$ 0.37	$ 0.22
Anti-dilutive equity awards not included in the detailed earnings per share computation
Equity awards not included in the diluted earnings per share computation	300,000	1,200,000