Stock - Based Compensation - Summary of Accumulated Stock Units (Detail) - $ / shares |
Mar. 31, 2016 |
Dec. 31, 2015 |
---|---|---|
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] | ||
Accumulated stock units | 67,558 | 66,376 |
Average price | $ 40.17 | $ 39.64 |