Capital Stock and Share-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended		1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended			3 Months Ended			12 Months Ended											12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Jun. 07, 2012 Maximum	Dec. 31, 2012 Maximum	Jun. 07, 2012 Minimum	Dec. 31, 2012 Stock Options	Dec. 31, 2011 Stock Options	Dec. 31, 2010 Stock Options	Jun. 30, 2012 Non-Vested Stock	Jun. 30, 2011 Non-Vested Stock	Jun. 30, 2010 Non-Vested Stock	Dec. 31, 2012 Non-Vested Stock Y	Dec. 31, 2011 Non-Vested Stock	Dec. 31, 2010 Non-Vested Stock	Dec. 31, 2012 Non Vested Stock Unit Y	Dec. 31, 2011 Non Vested Stock Unit	Dec. 31, 2010 Non Vested Stock Unit	Dec. 31, 2012 Employee Stock Purchase Plan	Dec. 31, 2011 Employee Stock Purchase Plan	Dec. 31, 2010 Employee Stock Purchase Plan	Dec. 31, 2012 Share-Based Awards M Y	Dec. 31, 2012 Share-Based Awards Maximum	Dec. 31, 2012 Share-Based Awards Minimum	Dec. 31, 2012 Share-based awards to more Than 10% owners Minimum	Dec. 31, 2012 Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized to issue	60,000,000	60,000,000
Common Stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized to issue	5,000,000	5,000,000
Preferred stock, par value	$ 0.001	$ 0.001
Common stock, shares issued	31,876,508	30,328,549																							31,086,619
Common stock, shares outstanding	31,086,619	29,639,735
Preferred stock, shares issued
Preferred stock, shares outstanding
Percentage of ownership in subsidiaries																					50.00%
Equity-based awards, maximum number of shares granted																						3,900,000
Equity-based awards, available for grant, shares																					2.7
Fair value of a share of common stock, percentage																							100.00%	110.00%
Percentage of total combined voting power of us and our subsidiaries																							10.00%
Equity-based award vesting period, minimum period												1			3						12
Equity-based award vesting period, maximum period												5			4						5
Contractual term of stock options exercised				Ten years
Percentage of fair market value at which eligible employees may purchase shares of common stock																		85.00%
Issuance of stock-employee stock purchase plan, shares	2,485,604		4,500,000		2,500,000
Stock available for future issuance																		2,014,396
Employee stock purchase plan expenses																		$ 0.7	$ 0.8	$ 1.1
Total intrinsic value of options exercisable						0.2
Total intrinsic value of options exercised						0.1	0.7	4.3
Stock compensation plan expense												6.4	7.2	7.6	0.1	0.3	2.0
Weighted average grant date fair value of non-vested stocks granted												$ 14.01	$ 27.05	$ 54.29	$ 56.99	$ 27.40
Unrecognized compensation cost related to non-vested stock award payments												$ 4.9
Non-vested stock award payments, weighted-average period, years												1 year 4 months 24 days
Number of stock units authorized for achievement of targeted performance									173,396	61,583	25,754
Number of stock units authorized for exceeding targeted performance									260,094	92,376	38,631
Performance based objectives, percentage of target met													79.50%
Performance based award share amount earned													17,023