Stockholders' Equity - Additional Information (Detail) - USD ($)					1 Months Ended				12 Months Ended
	Oct. 28, 2015	Jul. 29, 2015	May. 07, 2015	Feb. 19, 2015	Dec. 31, 2015	Nov. 30, 2015	Sep. 30, 2015	Oct. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Nov. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Shares authorized					300,000,000				300,000,000	300,000,000
Preferred Stock, Shares authorized					100,000,000				100,000,000	100,000,000
Preferred Stock, Shares issued					0				0	0
Preferred Stock, Shares outstanding					0				0	0
Issuance of common stock in public offering of common stock, shares						2,995,000
Issuance of common stock in public offering of common stock						$ 829,496,000			$ 829,496,000
Underwriting discounts and commissions incurred in issuance of common stock in public offering of common stock						32,344,000
Offering costs incurred in issuance of common stock in public offering of common stock						$ 660,000
Interest rate (percent)											8.125%
Total consideration for common stock repurchase										$ 297,958,000	$ 48,799,000
Treasury stock re-issued											6,000
Short term dividend payable					$ 13,674,000				13,674,000	4,559,000
Long term dividend payable					13,394,000				13,394,000	$ 4,972,000
Dividends declared per share (in dollars per share)	$ 1.69	$ 1.69	$ 1.69	$ 1.69
Dividends paid									393,584,000
Over-Allotment Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock in public offering of common stock, shares						391,000
Special Distribution [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Special distribution, amount							$ 627,000,000	$ 416,000,000
Special distribution, per share (in dollars per share)							$ 10.95	$ 7.57
Closing price measurement period (in days)							3 days	3 days
Value of shares distributed per share (in dollars per share)							$ 297.03	$ 224.45
Common stock shares issued							1,688,411	1,482,419
Common stock issued amount							$ 125,486,000	$ 83,266,000
Special distribution, payable date							Nov. 10, 2015	Nov. 25, 2014
Record date							Oct. 08, 2015	Oct. 27, 2014
Maximum percentage of total distribution payable to all stockholders								20.00%
Short term dividend payable					13,674,000				13,674,000
Long term dividend payable					$ 13,394,000				$ 13,394,000
2013 Share Repurchase Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount authorized under the share repurchase program											$ 500,000,000
Number of common stock shares repurchased during the period										1,517,743	288,739
Average price of common stock shares repurchased (in dollars per share)										$ 196.32	$ 169.01
Total consideration for common stock repurchase										$ 297,958,000	$ 48,799,000
2013 Share Repurchase Program [Member] | Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury stock re-issued (shares)									7,348
Treasury stock re-issued									$ 1,807,000
2011 Share Repurchase Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount authorized under the share repurchase program														$ 250,000,000
Number of common stock shares repurchased during the period												131,489	870,421
Average price of common stock shares repurchased (in dollars per share)												$ 101.64	$ 99.57
Total consideration for common stock repurchase												$ 100,030,000
Treasury stock re-issued (shares)										355,477	8,266	638,167
Treasury stock re-issued										$ 66,424,000	$ 811,000	$ 63,354,000
4.75% Convertible Subordinated Notes and 3.00% Convertible Subordinated Notes [Member] | 2013 Share Repurchase Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury stock re-issued (shares)										1,752,615
Treasury stock re-issued										$ 345,858,000
3.00% Convertible Subordinated Notes [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Interest rate (percent)					3.00%				3.00%	3.00%
4.75% Convertible Subordinated Notes [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Interest rate (percent)					4.75%				4.75%	4.75%
Shares issued in exchange for convertible subordinated notes					101,947
4.75% Convertible Subordinated Notes [Member] | 2013 Share Repurchase Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury stock re-issued (shares)									11,784
Treasury stock re-issued									$ 3,546,000
4.75% Convertible Subordinated Notes [Member] | 2011 Share Repurchase Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Interest rate (percent)										4.75%
2.50% Convertible Subordinated Notes [Member] | 2011 Share Repurchase Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Interest rate (percent)												2.50%
Series A [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Shares authorized					25,000,000				25,000,000
Series A-1 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Shares authorized					25,000,000				25,000,000
Undesignated [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Shares authorized					50,000,000				50,000,000