Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended
	Feb. 15, 2017	Mar. 31, 2017	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued and sold		6,069,444
Stock issued, new issues		$ 2,126,300
Proceeds from issuance of stock		57,900
Payments of stock issuance costs		800
Quarterly cash dividend declared (in dollars per share)	$ 2.00
Payments of dividends			$ 148,083	$ 124,836
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued in period			511,508
Weighted-average grant date fair value of shares issued (in dollars per share)			$ 367.22
Weighted average requisite service period of shares issued			3 years 5 months 24 days
Special Distribution [Member] | Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividends payable		$ 2,600	$ 2,600
Over-Allotment Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued and sold		791,666