Equity - Additional Information (Detail) (USD $)	3 Months Ended								12 Months Ended					1 Months Ended				12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Common Stock	Dec. 31, 2011 Common Stock	Apr. 30, 2010 Caliburn Acquisition	Apr. 30, 2010 Caliburn Acquisition Common Stock	Apr. 30, 2010 Caliburn Acquisition Contingent Convertible Preferred Stock	Apr. 02, 2010 Caliburn Acquisition Contingent Convertible Preferred Stock	Dec. 31, 2012 Restricted Stock Units	Dec. 31, 2011 Restricted Stock Units	Apr. 30, 2010 Tranche One - Performance Stock [Member] Caliburn Acquisition Contingent Convertible Preferred Stock	Apr. 01, 2013 Date of Conversion - Performance Stock [Member] Caliburn Acquisition Contingent Convertible Preferred Stock
Stockholders Equity Note [Line Items]
Dividends declared per common share	$ (0.45)	$ (0.45)	$ (0.45)	$ (0.45)	$ (0.45)	$ (0.45)	$ (0.45)	$ (0.45)	$ 1.80	$ 1.80	$ 1.80
Dividend equivalents paid on outstanding restricted stock units									$ 5,600,000	$ 4,800,000	$ 5,200,000
Dividend on restricted stock unit, restriction									In the event a restricted stock unit holder’s employment is terminated, a portion of the dividend equivalent may be required to be paid back to the Company.
Dividends paid back									$ 117,241	$ 360,769	$ 12,040
Acquisition date														Apr. 01, 2010
Shares issued in acquisition															1,099,874	1,099,877
Date of Conversion of Performance Stock																					April 1, 2013
Conversion to common stock shares if revenue targets are achieved																	1,099,877			659,926
Restricted stock units vested and issued as common stock																		654,612	654,000
Repurchased shares for award																		181,820	283,774
Average repurchase price of shares for award																		$ 45.29	$ 67.19
Repurchased common stock												1,714,614	1,068,719
Average repurchase price of common stock												$ 43.70	$ 43.71