Schedule of Common Stock Repurchases (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Stockholders Equity Note [Abstract]
Shares repurchased	25,398			76,299			174,211	479,922
Cost of shares repurchased (in millions)	$ 19,294	$ 12,666	$ 80,486	$ 45,950	$ 214,835	$ 21,268	$ 112,400	$ 282,100
Average price per share repurchased	$ 759.70			$ 602.24			$ 645.46	$ 587.70

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

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